The 10 Senate seats most likely to flip in 2024

By Simone Pathe, CNN

(CNN) — Democrats faced a challenging path to holding their Senate majority even before President Joe Biden stepped aside from the 2024 campaign – and they likely still do with Vice President Kamala Harris as their presumptive nominee.

But this year’s Democratic candidates, many of them well-known incumbents, have so far been able to create some separation from the top of the ticket. The question is whether they can sustain it as these contests take off over the late summer and fall.

Nine of the top 10 seats on CNN’s latest ranking of the Senate seats most likely to flip are held by Democrats (or independents who caucus with them). And assuming Republicans flip West Virginia, where Sen. Joe Manchin is retiring, the GOP just needs to win the White House or pick up one more Senate seat to win the majority.

That’s a tough landscape for Democrats – especially when they’re defending seats in states that either twice voted comfortably for Donald Trump (Montana and Ohio) or are presidential battlegrounds. CNN polling released this week showed no clear leader between Harris and the former president – although it was closer contest than CNN had found in earlier surveys of the Biden-Trump matchup. The poll showed Harris doing better than Biden against Trump among some key demographic groups – younger voters, female voters and Black voters.

But there’s been limited public polling of Senate races that would capture the past tumultuous month in American politics – from the June 27 presidential debate that sparked Democratic consternation about Biden, the assassination attempt on Trump in Pennsylvania in mid-July, and Biden’s decision to forgo reelection nearly a week ago.

The CNN poll found Trump enjoying his highest approval rating since 2020 in CNN surveys and maintaining support with his most loyal constituencies. Republicans have already made clear they’ll be tying Harris to the Biden administration, misleadingly calling her a “border czar” because of her assignment to address the root causes of emigration from Central America. Even though her role has not included managing the border, that messaging fits into the immigration-related attacks that have been central to GOP campaigns this cycle.

The National Republican Senatorial Committee said in a memo this week that “Harris is arguably a bigger threat to Democrats’ Senate majority than Joe Biden,” acknowledging that the narrative about the president’s mental fitness didn’t apply as well to down-ballot races. The committee encouraged candidates to tie senators to Harris and her positions.

All of that raises the stakes for Senate Democrats to keep doing what they’re doing: touting their legislative accomplishments without invoking the Biden administration and using their fundraising edge to try to define their GOP challengers – often by mining their business backgrounds and out-of-state ties. Democrats have also been hitting back on attacks over the southern border by highlighting their support of bipartisan immigration legislation that Republicans killed in Congress this year.

But the risk for Democrats is that as their Republican challengers become better known, GOP campaign spending increases and more voters tune in, any separation from the top of the ticket will erode. Ticket-splitting isn’t as common as it once was, as CNN political analyst Ronald Brownstein wrote recently.

One change to this month’s CNN ranking is reflective of that challenge. Two Democratic-held seats are trading places: Michigan, an open seat, moves above Pennsylvania, where there’s a three-term incumbent on the ballot. But otherwise, the list remains unchanged from April, when Maryland was first included due to Republican former Gov. Larry Hogan’s candidacy and when Florida fell off. That leaves Texas as the only Democratic target in the top 10.

While Biden was still a candidate, his recent struggles had raised questions about whether the list of Senate GOP targets would grow – a source of enthusiasm for attendees at last week’s Republican National Convention. Virginia GOP nominee Hung Cao, for example, addressed the delegates just as new polling from The New York Times/Siena College showed a margin-of-error presidential race in the Old Dominion. (Democratic Sen. Tim Kaine, however, led Cao 53% to 36% among likely voters in that survey.)

And NRSC Chair Steve Daines talked up the prospects of New Mexico nominee Nella Domenici, the daughter of the late Sen. Pete Domenici. Democrats, however, felt confident about their incumbents in states Biden won by 10 points (Virginia) and 11 points (New Mexico), given that some of their candidates in much tougher states are, for now, still holding their own. But if Harris can keep the race with Trump tighter, the Senate map is less likely to expand in the GOP’s favor.

The rankings below represent a snapshot of where the race for the Senate stands and not necessarily where it may be heading, so we’ll check back on the following contests next month.

1. West Virginia

Both Democrats and Republicans have essentially been treating this seat as a GOP pickup since Sen. Joe Manchin announced he wasn’t running for reelection. The onetime Democratic senator tried last month to put to rest chatter that he could run as an independent against Republican nominee Jim Justice, the current governor, in the Trump-friendly state. “I’m not running for any office, political office,” Manchin told CNN’s Manu Raju in June shortly after registering as an independent. He did, however, leave a little bit of wiggle room ahead of the August 1 filing deadline, adding, “You always have options, because life is full of surprises.”

Justice, a former Democrat, has had his share of troubling headlines – about his business practices, for example – but he’s a popular and well-known second-term governor who easily dispatched Rep. Alex Mooney in the May Republican primary. And Manchin, the most conservative member of the Senate Democratic Caucus, was clear about the challenge of running in a state that’s moved so sharply to the right, noting that the “D” brand in West Virginia had grown “toxic.”

2. Montana

Sen. Jon Tester needs to overperform the top of the ticket in a state that twice backed Trump by double digits. Tester has won tough elections before – including in 2018, when Trump was in the White House – but this is the first year he will be on the same ballot as the former president.

Republicans have run plenty of ads attempting to tie Tester to Biden and attacking him over the border. They are now likely to substitute the president for Harris, although Tester is among the few Democrats not to have endorsed her so far. Democrats, meanwhile, are trying to play up the contrast between the seven-fingered dirt farmer and his GOP opponent, Tim Sheehy, a wealthy businessman and retired Navy SEAL. Last Best Place PAC, a Democratic-aligned group, has run ads poking fun at what they call Sheehy’s “hobby ranch” and attacking him as a “millionaire out-of-stater driving up housing costs.” Democrats have also seized on Washington Post reporting about Sheehy’s changing account of a gunshot wound sustained roughly a decade ago to raise questions about his credibility.

The relevance of Sheehy’s relatively recent arrival in the state – he settled there in 2014 after leaving the military – has become a key question in this race. Democrats are trying to make it a weakness after using a similar argument to discredit Republican nominee Matt Rosendale in his 2018 challenge to Tester. But Republicans argue that post-pandemic Montana is filled with conservative transplants from bluer states and that Sheehy, who recently stepped down as CEO of Bridger Aerospace, has been a job creator.

Tester raised $10.6 million in the second quarter – about double Sheehy’s haul, which included a million dollars in personal loans. The senator spent more than he took in those three months, but he still started July with a healthy cash-on-hand advantage over Sheehy – $10.9 million to his opponent’s $3.2 million.

3. Ohio

Democratic Sen. Sherrod Brown is the second-most vulnerable incumbent, facing reelection in a state that Trump has twice carried by 8 points. His path to reelection, like Tester’s, runs through distancing himself from the top of the ticket while trying to paint a character contrast with his GOP opponent to localize rather than nationalize the race. Democrats got their preferred opponent in Bernie Moreno, a Cleveland car dealership owner whom they boosted in a three-way primary by highlighting his backing from Trump.

Brown, a progressive populist who’s been in Congress since 1993, raised more than any other incumbent in the second quarter and is spending heavily – a whopping $18.1 million during that three-month period – to shape that contrast with Moreno. His ads feature a Republican sheriff vouching for him and tout successful legislation to lower the cost of insulin (without mentioning that this was a Biden priority). A Democratic-aligned outside group has highlighted legislation he has pushed that Trump signed. Democrats have been working to define Moreno – Brown’s campaign uses his background as a car dealer to attack his credibility, for example. Democrats have also seized on a New York Times story that poked holes in the personal narrative the Colombian-born Moreno presents on the trail.

Brown is the known commodity in this race – a recent ad about his gravelly voice underscores that familiarity – but Republicans think Ohio voters will eventually come their way given the state’s increasing redness. Moreno, who’s playing up his ties to Trump’s running mate, Ohio Sen. JD Vance, had tried to tether his opponent to an unpopular president with one ad featuring two men, supposed to be Biden and Brown, riding a tandem bicycle to make the argument that they’re pedaling together in Washington.

A Marist poll released in early June, well before Biden dropped out, hinted at the ticket-splitting Democrats are banking on for Brown to prevail. (While Trump led Biden by 7 points among registered voters, Brown led Moreno by 5 points.) Brown, who raised $12.8 million in the second quarter and ended June with $10.7 million in the bank, will need to similarly overperform Harris to win another term. Moreno raised $4.4 million and ended the quarter with $4.5 million on hand.

4. Nevada

Democratic Sen. Jacky Rosen is running for a second term in a state that, on paper, would seem to lean more comfortably blue (Biden carried it by 2 points) than a few others on this list. But the first-term senator, who’s up against Republican Sam Brown, may be in a more vulnerable position than some of her fellow battleground state incumbents in part because of the state’s shifting demographics.

Rosen led Brown 47% to 40% in a Times (UK)/SAY24/YouGov survey released last week. Before that, the most recent poll that met CNN standards – from The New York Times/Siena College in early May – had each Senate candidate at 41%.

Rosen, who raised $7.6 million in the second quarter and spent nearly $4 million more than that, is touting her work to lower prescription drug costs (again without mention of Biden). But she doesn’t have the same established brand as her Montana or Ohio colleagues. She’s trying to tar Brown as a “MAGA extremist” – specifically attacking inconsistencies in his abortion position, which Democrats see as an especially salient issue in the Silver State. Brown, who told NBC News earlier this year that he’d “close the door” on backing a national abortion ban and that he supported Nevada’s law allowing the procedure up to 24 weeks, once backed a more restrictive abortion bill when running for office in Texas. His support for that legislation, and its effect on one woman named Valerie, was the subject of one of Rosen’s first ads against the Army veteran after he won the GOP nomination last month.

Brown, who got a shout-out from Trump during his keynote speech at the Republican convention last week, is focused on the border and the economy, promising to build Trump’s wall and extend his tax cuts. He raised $4.1 million in the second quarter, ending with $3.1 million in the bank to Rosen’s $9.5 million.

5. Arizona

While Arizona has looked favorable for Republicans at the presidential level, their liability at the Senate level is their leading candidate. Kari Lake, who lost the 2022 gubernatorial election and continues to make false claims about that defeat and the 2020 election, is all but guaranteed to win the GOP nomination in the August primary to succeed retiring independent Sen. Kyrsten Sinema.

Lake would then be up against Democratic Rep. Ruben Gallego, who significantly overperformed Biden in the Times (UK)/SAY24/YouGov poll conducted after the presidential debate but before the assassination attempt on Trump. While Trump led the president 44% to 37% among registered voters, Gallego led Lake 48% to 41%. Harris may have the ability to do better in a state like Arizona, which Biden barely flipped in 2020, but it remains to be seen how her candidacy will affect the Senate race. Gallego, a Marine veteran, went up on TV early, giving him an advertising advantage that’s been fueled by his strong fundraising. He brought in nearly $10.5 million in the second quarter to Lake’s $4.3 million and started July with $9.2 million in the bank to his opponent’s $2.8 million.

A former member of the Congressional Progressive Caucus, Gallego is attempting to cut a more moderate profile in this race, with ads that tout his military service, his humble upbringing and his work to lower costs for families. Lake has run ads with the NRSC that feature women talking about their fears of the border and immigrants. But she’s faced concerns from within her own party – including from Trump, according to The Washington Post – that she’s traveling the country too much instead of campaigning in the state she’s trying to win. If Trump does well enough in Arizona, however, he may be able to carry Lake to victory with him.

6. Michigan

The race to replace retiring Democratic Sen. Debbie Stabenow in Michigan – where Republicans haven’t won a Senate race in 30 years – moves up one spot on the ranking this month. That’s largely because it’s an open seat, which is typically harder for the party in power to defend while facing a troubling national environment.

Democratic Rep. Elissa Slotkin, who’s all but guaranteed to win next month’s primary, is a strong recruit and fundraiser – she raised $6.5 million in the second quarter and ended June with $9.6 million in the bank. But her comments on a donor call, obtained earlier this month by The New York Times, crystalized the Democratic fears about how the top of the ticket could jeopardize such a crucial battleground race. Slotkin said that Trump was leading in her state and that the Senate race was a toss-up. But Slotkin acknowledged on CNN this week that her race was in a better position without Biden running. In particular, she said “the energy is palpable” for Harris, citing enthusiasm she’d heard from young voters.

Polling from the Times (UK)/SAY24/YouGov showed Slotkin holding her own against the likely Republican nominee, former Rep. Mike Rogers – 48% to 39% among registered voters.

Notably, both candidates have national security backgrounds – Slotkin as a former CIA analyst and Rogers as the former chairman of the House Intelligence Committee. Slotkin has made her public service a cornerstone of her campaign and advertising, touting her experience in Democratic and Republican administrations.

With the primary still looming, Rogers’ allies are leaning into his endorsement from Trump. A recent ad from the Great Lakes Conservatives Fund, for example, almost exclusively features the former president praising Rogers. Rogers raised $2.1 million in the second quarter, ending June with $2.5 million banked.

7. Pennsylvania

Democratic Sen. Bob Casey, a three-term incumbent with a well-known name in the state, is facing wealthy Republican Dave McCormick – a matchup that both sides are trying to milk for the political contrast that suits them. For Democrats, that means painting McCormick, a onetime hedge fund executive, as a rich guy who regularly flies back to Connecticut, has had business ties to China and opposes abortion rights.

For Republicans, it’s been about portraying Casey as a career politician who answers only to Washington and who is weak on the border. McCormick’s campaign quickly pivoted this week to attacking the “Harris-Casey agenda,” releasing a digital video that splices past footage of Harris and calls her “the most liberal nominee ever.”

Democrats have been trying to counter the border message. For example, one ad from Duty and Honor sounds like it could be a GOP spot, opening with “Fentaynl and crime, they’re coming from our southern border.”

Before Biden dropped out, Casey had been holding his own, even as the numbers for the president – who narrowly carried the state in 2020 – became more precarious. A New York Times/Siena College poll conducted after the presidential debate but before the assassination attempt on Trump found Casey leading McCormick 50% to 42% among likely voters while Biden and Trump were locked in a close race.

Casey raised $8 million in the second quarter, entering July with $8.4 million on hand. McCormick raised $6.7 million, which included $2.1 million in personal loans, ending June with $8 million. But he has plenty more of his own money to spend, as well as a supportive super PAC, and the Senate Leadership Fund recently announced a $24 million investment in the state beginning in September – a sign that Republicans see this as a winnable contest.

8. Wisconsin

Sen. Tammy Baldwin was with Harris in Milwaukee this week for the vice president’s first campaign rally since becoming the presumptive Democratic nominee – a clear sign that down-ballot Democrats feel better about their chances with Harris on top of the ticket.

Biden barely won the Badger State in 2020 after Trump had carried it by a similarly narrow margin four years earlier. Despite those thin margins, Democrats are heartened that Baldwin, a two-term senator with a known statewide brand, will likely be up against Republican Eric Hovde, the favorite in the August primary.

Hovde has made a string of controversial comments that have provided fodder for Democrats as they rush to define him. Baldwin’s campaign has run ads with people responding to a remark he made during a 2012 Senate run that those who are overweight need to pay more for health care and to a more recent comment that most nursing home patients aren’t in a condition to vote.

Hovde, the CEO of Sunwest Bank who bought a house in Laguna Beach, California, after losing the 2012 Senate primary, has responded to Democratic attacks about his out-of-state ties with an ad that showcases where he grew up and went to school in Wisconsin. Hovde ran ads trying to press Baldwin to say whether she thought Biden should step aside, which she did not. After Biden dropped out of the race, Hovde attacked the senator for not taking a firm enough stand, accusing her of being part of a “Biden cover-up.” (Asked about Biden last week, before his announcement, Baldwin said she was hearing “legitimate and serious concerns” about the president from her constituents and relaying them to the White House and the Biden campaign.) She has also been on the air touting her work to cap insulin prices and crack down on fentanyl.

Pointing to Hovde’s early spending, Daines, the NRSC chairman, said at an RNC event last week that the Wisconsin Republican has closed the gap with his Democratic opponent more than any other GOP challenger. That’s where self-funding comes into play. Hovde’s second-quarter haul was just slightly less than Baldwin’s – $7.3 million to $7.5 million – but his total included a $5 million loan. Baldwin ended June with $7.3 million in the bank, while Hovde had $5.4 million.

Baldwin led Hovde 50% to 43% among registered voters in the Times (UK)/SAY24/YouGov poll. A Marquette Law School poll from mid-June showed the senator up 52% to 47% over Hovde among both registered and likely voters. Notably, however, Hovde was still largely unknown – 44% of registered voters said they hadn’t heard enough about him to form an opinion, which means he likely has room to grow his support.

9. Maryland

Angela Alsobrooks shook up the political world this spring when she defeated self-funding Rep. David Trone for the Democratic nomination to succeed retiring Democrat Ben Cardin. She’ll now face Republican former Gov. Larry Hogan, who’s the only reason a seat in a state Biden carried by more than 30 points is even competitive.

While Alsobrooks, the executive of Prince George’s County, doesn’t bring the personal resources that Trone would have, she has proved to be a strong campaigner and has raised significant money. She narrowly outraised Hogan in the second quarter, raking in $5.3 million to his $5.1 million, and ended up with more money in the bank. Alsobrooks’ potential to become the first Black senator from Maryland and just the third Black woman elected to the Senate carries appeal for some voters – especially against a White Republican opponent whom Democrats are attacking on abortion.

Hogan has tried to distance himself from his party – “In the Senate, Republicans can’t count on my vote,” he says in one spot. After winning his primary, he told The New York Times that he’d support federal legislation to codify Roe v. Wade – which Alsobrooks immediately criticized, citing his previous veto of a state law to expand abortion access. Hogan has also tried to disavow his June endorsement from Trump, saying he had “no interest” in it. But Trump’s embrace of the former governor – who has said he isn’t backing the former president – may be a gift for Democrats trying to defend this seat.

10. Texas

Knocking off Sen. Ted Cruz in Texas was going to be a tough proposition for Democrats regardless of whom they nominated for president. Democrats have not won a statewide election in Texas since 1994. Still, Democrats have a strong recruit in Dallas-area Rep. Colin Allred, who first came to the House by unseating a Republican congressman in 2018.

Allred’s campaign pulled in more than Cruz’s principal campaign account in the second quarter, although the senator still ended with more cash on hand. Allred brought in $10.5 million, spent about as much and ended June with around the same amount in the bank. Cruz raised $7.9 million and ended the period with $12.7 million banked.

Despite Texas voting reliably red, polling of the Senate race has shown a close contest – 47% of likely voters backed Cruz and 44% backed Allred in a recent University of Houston/YouGov poll.

This story has been updated with additional information.

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