The 10 Senate seats most likely to flip in 2024

By Simone Pathe, CNN

(CNN) — If there was one sign this week of Vice President Kamala Harris’ place atop the Democratic ticket having improved the party’s brand, it was the presence of so many Senate candidates taking the stage at its convention in Chicago.

Notably, three of the most vulnerable senators skipped the Democratic National Convention. But nominees in Michigan, Arizona, Pennsylvania, Wisconsin, Maryland and Texas were on hand for at least part of the week, with many of them speaking the same night as Harris.

While Harris has improved on President Joe Biden’s standing in many states — putting Nevada and Arizona back in play, for example — the basic shape of the crucial Senate races that will determine the majority is the same. Democrats were overperforming the top of the ticket when Biden was the nominee and they still are under Harris.

But Democrats are facing an incredibly unfavorable map this year, defending seats in places that former President Donald Trump won by comfortable margins and presidential battlegrounds that he narrowly lost in 2020. Assuming Republicans pick up West Virginia, where Sen. Joe Manchin is retiring, the party just needs to win the White House or pick up one more Senate seat to secure the majority.

And underneath the topline trend of Democratic overperformance (so far), there are emerging differences among some of these races that have resulted in shifts to this month’s ranking of the Senate seats most likely to flip, which is based on CNN’s reporting, as well as fundraising, polling and spending data.

The top three states most likely to change hands — West Virginia, Montana and Ohio — aren’t budging. After those three, the next most likely are now open seats where Democrats are on defense: Michigan and Arizona. Seats without incumbents are almost always harder to defend, in part because the nominees don’t have as well-known brands to help buck any national headwinds. Those two seats slide above Nevada, where Sen. Jacky Rosen is running for a second term and which had previously been No. 4.

While Harris has been riding several weeks of momentum (and, if history is any guide, will likely see some sort of post-convention polling bump), there’s still a long road to November — with a looming September 10 debate against Trump and promises to eventually sit for a one-on-one interview, among other things, that could shake up the 2024 race.

And at the Senate level, as more voters tune into the election heading into the traditional post-Labor Day campaign season and more Republican spending ramps up, both parties expect numbers in their races to tighten. There’s only one Democratic pickup target on the list (Texas), while Republicans are still optimistic about expanding the map into New Mexico, which has not made the list.

The rankings below represent a snapshot of where the race for the Senate stands now — and not necessarily where it may be heading — so we’ll check back on the following contests as things develop.

1. West Virginia

No news here: West Virginia is still the seat most likely to flip — a reality Democrats have long acknowledged.

It would have been a tough seat to hold even with Manchin, but without the Democrat-turned-independent senator running for reelection, Republican Gov. Jim Justice is poised to be the next senator from a state Trump is expected to carry by double digits.

2. Montana

Sen. Jon Tester remains the most endangered Democrat running for reelection. In a state Trump twice carried by significant margins, he’ll likely need to overperform Harris by double digits. That’s an extremely tall order, but the seven-fingered dirt farmer has a history of defying the partisan lean of his state. What’s different this year, however, is that it’s the first time he’s on the ballot at the same time as Trump. Republican ads repeatedly played footage of the senator saying he endorsed Biden. And although Tester did not attend the DNC and said this week he won’t be endorsing in the presidential race, Republicans are continuing to try to tie him to an administration that’s deeply unpopular in Montana.

While Republicans try to nationalize the race, Democrats are trying to underscore the contrasts between Tester and his GOP challenger Tim Sheehy, a retired Navy SEAL. They’re running a similar playbook against him as they did against Matt Rosendale in 2018, trying to paint him as an out-of-state millionaire who would threaten access to public lands and questioning his ranching credentials. Sheehy settled in Montana in 2014 after leaving the military, and Republicans argue those carpetbagging attacks only go so far now that there are more conservative transplants in the state after the pandemic.

One new wild card in the race: Montana will now have an abortion measure on the November ballot. Democratic Senatorial Campaign Committee Chairman Gary Peters expressed confidence in Chicago last week that the referendum would boost Tester.

3. Ohio

Democratic Sen. Sherrod Brown’s place on the list has been consistent — besides Tester, he’s the most vulnerable senator because he, too, is running for reelection in a Trump state. He’s likely in a slightly safer position than Tester given Trump’s narrower margins in the Buckeye State. First elected to the Senate in 2006, Brown’s brand of progressive populism has allowed him to defy Ohio’s increasing redness. And he’s not shy about touting his work across the aisle. “That’s why I’m partnering with Republicans to block China from purchasing more farmland,” he says in a recent spot about protecting Ohio jobs and farms. Another features a Republican sheriff vouching for Brown’s efforts to fight fentanyl coming across the border — a frequent tactic this year for Democratic incumbents trying to get ahead of GOP attacks.

This year, Brown is up against Republican businessman Bernie Moreno, whom Democrats boosted in the GOP primary because they thought he’d be the weakest opponent. They may have been correct. The car dealership owner trailed Brown even when Biden was atop the ticket. That doesn’t mean that Brown is safe, however. Moreno is just now stepping up his ad spending, which will likely make things more competitive. He’s running a spot with the National Republican Senatorial Committee that focuses on immigration — specifically blaming Brown for the border crisis and trying to tie him to Harris. In the contrast spot, he reminds voters that he’s backed by Trump — a potentially powerful argument in this state even if Moreno himself isn’t well known.

4. Michigan

The race to replace retiring Democratic Sen. Debbie Stabenow moves up two spots on the list because it’s an open seat, which is typically harder to defend. When Biden was still defying his party’s entreaties to step aside, Democratic Rep. Elissa Slotkin raised alarm bells about the direction of the contest in this crucial blue wall state. The three-term congresswoman has praised the new energy Harris has brought to the race. But as a congresswoman running statewide for the first time, she’ll face a challenging race against Republican former Rep. Mike Rogers.

Slotkin, a former CIA analyst, is an impressive fundraiser whose ads tout her service under the Bush administration. But Rogers also brings national security experience to the race as the former chairman of the House Intelligence Committee. Slotkin went negative against him as soon as he won the August 6 GOP primary, blasting him as a career politician who’s looked after himself. The DSCC is striking a similar tone in an ad called “Florida man” (a nod to his Sunshine State property) that says he’s “in it for Mike, not for Michigan.”

The day Slotkin spoke at the DNC, the NRSC debuted a new ad against her featuring a Republican sheriff saying that law enforcement needs a senator “who has our back.” (While the ad attacks her of voting against GOP-sponsored border security measures last year, she supported this year’s bipartisan border security bill that Trump leaned on the GOP to kill.) Republicans are also trying to tie her to Covid relief funds gone wrong.

Slotkin was at 46% to Rogers’ 43% among likely voters in an early August New York Times/Siena College poll, with more independents breaking for the Republican. Harris was at 50% to Trump’s 46%. (Both results were within the margin of error.)

5. Arizona

Arizona, another open-seat race Democrats are trying to defend, remains at No. 5. But it’s now above Nevada because of the open seat and because it is a state where the border — a strong issue for Republicans — is front and center.

Sen. Kyrsten Sinema, who became an independent but still caucuses with Democrats, is not running for reelection. Her departure from the race gave way to a two-way matchup between Democratic Rep. Ruben Gallego, a Marine veteran, and Republican Kari Lake, a Trump ally who hasn’t let go of claims that she actually won the 2022 gubernatorial election.

Democrats’ victory here in 2020 — for both the White House and the Senate — established Arizona as a purple state. It looked less competitive at the top of the ticket when Biden was still running, but Harris seems to have put the Sun Belt States back in contention. A New York Times/Siena poll in mid-August found a tight race between her and Trump.

Even when Trump was ahead, though, some Republicans were anxious about Lake, who’s proven to be a controversial candidate unwilling to moderate many of her positions to appeal to the state’s suburban and independent voters. She’s even alienated members of her own party, which the DSCC has tried to highlight in an ad that plays footage of her attacking the late Sen. John McCain. But she scored a powerful endorsement this month from former Gov. Doug Ducey, who had backed her 2022 primary challenger. His support speaks volumes about the party’s willingness to get behind Lake if it means they might be able to hold this seat again.

Gallego led Lake by 9 points among likely voters in that same New York Times/Siena poll. But by the numbers, this is still a tough state for Democrats, where Gallego — a former member of the Congressional Progressive Caucus — will need to win over some voters from across the aisle. He was pulling 12% of registered Republicans and more than half of independents in the Times poll. This is another state where Democrats hope a ballot measure on abortion rights could boost their chances.

6. Nevada

Nevada, where Rosen is running for a second term, drops down two spots this month — in part because Harris has improved the party’s fortunes at the top of the ticket.

As an incumbent, Rosen may be in a better position than some Democrats elsewhere who are running statewide for the first time. She doesn’t have the strong brand that her colleagues in Montana or Ohio do, but she led Republican Sam Brown by 9 points among likely voters in a New York Times/Siena poll. That margin will undoubtedly tighten as more voters get to know Brown, an Army veteran who first ran for office in Texas, then lost last year’s GOP Senate primary in Nevada. And it’s still tough terrain for Democrats, with a transient population and demographics that may be moving away from the party.

But abortion is also on the ballot in Nevada, a state where Democrats believe reproductive rights are particularly salient. Brown’s messaging hints at that, too — he and his wife have spoken about her decision to have an abortion when she was 24 and single, and Brown has said that he’d “close the door” on backing a national ban. He also said he supports the Nevada law that allows abortions up to 24 weeks. Democrats, however, have tried going after inconsistencies in his abortion stance, including his support for more restrictive legislation in Texas.

7. Pennsylvania

Democratic Sen. Bob Casey’s seat remains the 7th most likely to flip. The three-term Democrat has enjoyed an edge over GOP challenger Dave McCormick for much of this year, and that’s still the case as he’s continued to overperform the top of the ticket in this crucial battleground.

As of mid-August, Casey led McCormick 52% to 44% among likely voters in a Quinnipiac University survey. (Harris was at 48% to Trump’s 45% among likely voters.) And a New York Times/Siena poll taken around the same time showed Casey striking above 50% — a notable threshold for the incumbent, even if his 14-point edge among likely voters in that poll is probably too rosy for the Democrat.

Casey, a well-known incumbent with a familiar last name in Pennsylvania politics, was winning 14% of registered Republicans in that Times poll and more than half of independents. He and his Democratic allies have been attacking McCormick, who lost last year’s GOP Senate nod, over his business ties to China as a former hedge fund executive. The Casey campaign is even using sound of Trump during that 2022 primary calling McCormick, whom he’s endorsed this year, a “Wall Street Republican” and “absolutely the candidate of corporations and special interests.”

Underscoring McCormick’s challenge, 37% of voters in the Quinnipiac survey said they hadn’t heard enough about him to form an opinion. But that also represents an opportunity for the Republican to grow, especially as his millions — and those of his allies — begin to saturate the airwaves. They’re hitting Casey hard on immigration and trying to tie him to the Biden-Harris administration on the border and inflation.

8. Wisconsin

Democratic Sen. Tammy Baldwin’s appearance with Harris at her first campaign rally as the presidential nominee said a lot about how the change at the top of the ticket relieved some congressional candidates. The two-term senator, who’s facing her most competitive reelection, hadn’t appeared with Biden at his post-debate rally in the state.

She’s up against Republican Eric Hovde, who has put $13 million of his own money into his campaign and quickly pivoted from trying to tie her to Biden to trying to tether her to Harris. Even when Biden was the nominee, though, Baldwin was holding her own here as a well-known incumbent who visits rural and conservative parts of the state. In a mid-August New York Times/Siena poll, she led Hovde 51% to 44% among likely voters, while Harris (50%) and Trump (46%) were in a closer race. In an earlier Marquette Law School poll, taken just after Biden dropped out of the race, Baldwin was at 52% to Hovde’s 47% among likely voters.

As they are against other self-funding Republicans this year, Democrats are attacking Hovde — the CEO of Sunwest Bank — as an out-of-state millionaire with a home in Laguna Beach. “We have a Green County. We have a Brown County. We do not have an Orange County,” is a favorite stump line of Baldwin’s, alluding to Hovde previously being named one of the most influential people in the Southern California county.

Hovde is featuring his wife in a recent ad, calling out Baldwin for what she says is the senator’s “dirty campaign.” But the spot underscores a fear of some Republicans — that their nominee has spent too much time reacting and not enough time talking about issues that matter to voters. He is also trying to humanize himself in new spots, highlighting his diagnosis with multiple sclerosis at age 27.

9. Texas

Texas is the only Democratic offensive opportunity on this list. Rep. Colin Allred is trying to knock off GOP Sen. Ted Cruz in a reliably red state. And although it is still a longshot, Texas slides up one spot this month given national Democrats’ improving fortunes in some other places with Harris leading the ticket.

There’s been plenty of buzz (and money) around previous efforts to defeat Cruz, but Democrats think that Allred, as a former NFL player who flipped a GOP district in 2018, is a more viable challenger. He’s consistently kept polling close this summer. About 47% of likely voters said they’d back Cruz, while 45% said Allred in a University of Houston/YouGov poll. Harris trailed Trump by 5 points in the same survey — an improvement over Biden’s position in the state earlier this summer.

Allred, who also spoke at the DNC, is another Democrat hoping the issue of abortion — in particular, the backlash to Texas’ ban — could help him win over voters who might not have been otherwise inclined to vote blue. “It’s gotten more dangerous to be a woman in Texas,” an ob-gyn says in one Allred digital spot. “And it’s Ted Cruz’s fault,” adds another. (As a senator in Washington, Cruz did not actually vote for Texas’ legislation, although he has defended it.) Cruz, meanwhile, is leaning into the border, arguing in a contrast spot that also compares himself to Texas Toast that he is the one fighting for the state.

10. Maryland

Harris’ ascendance to the top of the ticket has boosted what was already strong enthusiasm among Black woman in Maryland for sending Angela Alsobrooks to the Senate to replace retiring Sen. Ben Cardin. And that’s important, Baltimore Mayor Brandon Scott told CNN in Chicago last week, because of how key Black women are to the Democratic vote in this overwhelmingly blue state.

Biden carried it by more than 30 points in 2020, so it was never a question of whether a Democrat would win the presidential race here. Maryland first joined the list of Senate seats most likely to flip because of the candidacy of Larry Hogan, who left two terms as governor as a popular Republican in the state. And while there hasn’t been any polling here that meets CNN standards since the primary, this race is moving down one spot for now, largely because of the enthusiasm for Harris and how closely it’s now tied to Alsobrooks, a mentee of the vice president who touted both of their prosecutorial backgrounds during a keynote address at the DNC.

While the convention drew attention to the history Alsobooks would make as the first Black person Maryland sends to the Senate (and only the third Black woman elected to the chamber), she — like Harris — has been leaning more into issues than her identity. A recent ad, for example, touts that she oversaw a drop in crime.

Hogan is trying to distance himself from the national GOP. In an ad from his campaign and the NRSC, for example, he says he’ll restore a woman’s right to choose and “fight the extreme Project 2025” — notable rhetoric for a Republican that sounds a lot more like the language heard in Chicago last week. National Democrats, meanwhile, are arguing that Hogan would be a 51st vote for Republicans in the Senate, highlighting his endorsement from Trump. (Hogan has said he’s not voting for Trump and isn’t interested in his backing.)

This story has been updated.

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