The 10 Races That Will Determine Control of the Senate

As the presidential race between Donald Trump and Kamala Harris remains tightly contested, the battle for Senate control is equally competitive, hinging on a handful of critical races across key states.

With 34 Senate seats up for election this November, Democrats are focused on defending their slim majority. Currently holding 51 seats, they face the prospect of losing a seat in red West Virginia that has been occupied by Sen. Joe Manchin since 2010. If that happens, Republicans would need just one additional victory to reclaim control of the chamber, provided they manage to avoid any upsets elsewhere.

The stakes are incredibly high. The party that controls the Senate will have power over the next president’s legislative agenda, Cabinet appointments, judicial nominations, and more. 

Here's a closer look at the ten key races that will determine control of the Senate.

Montana

Montana's Senate race is shaping up to be a critical test for Democratic incumbent Jon Tester, who faces a tough re-election campaign against Republican nominee Tim Sheehy, a retired Navy SEAL backed by Trump. 

In a state that Trump won by 16 points in 2020, Tester’s incumbency has given him a slight boost, but he will need to appeal to a diverse electorate, including independents and moderate Republicans. The most recent Emerson College poll—from early August—showed Sheehy ahead of Tester by just two points. (Montana is not polled very often as it’s not a presidential swing state).

Many political analysts consider Montana’s race to be the most critical bellwether contest for determining control of the Senate this cycle. The Cook Political Report recently shifted its rating of the race from toss-up to ‘Leans Republican,’ while other analysts are waiting for more reliable polling data. Tester has defied the odds before, winning red Montana in 2006, 2012, and 2018—all strong Democratic cycles. Lately he has leaned more into the abortion rights issue, which is on the ballot in Montana this year. His campaign has also focused on Sheehy’s use of racial stereotypes to refer to Native Americans—a small but important voting bloc in Montana—while Sheehy aims to portray Tester as an out-of-touch Washington politician tied to the national Democratic brand. (Tester has not endorsed a candidate for President.)

Michigan

All eyes will be on battleground Michigan this November—and not just for the presidential election. The high-stakes race to succeed retiring Democratic Sen. Debbie Stabenow is shaping up to be one of the most competitive in the nation, with the potential to tip the balance of power in the Senate. 

A September New York Times/Siena College poll shows that Democrat Elissa Slotkin, a third-term congresswoman, currently holds a narrow five-point lead over former Republican Rep. Mike Rogers. But unlike all the other Democratic candidates in key races on this list, Slotkin is getting a lower share of the vote than Harris, suggesting that Michigan could present the toughest challenge for Democrats to run ahead of the presidential race.

Given that neither of the candidates are well-known incumbents, their success largely hinges on how Harris and Trump perform in the “blue wall” state that Trump won in 2016 but Biden carried in 2020. Rogers, who was once a Trump critic but later won his endorsement, has been hitting Slotkin on inflation and the southern border, claiming she’s part of a “Biden-Harris-Slotkin” regime. Slotkin, meanwhile, has positioned herself as the “normal” and “rational” candidate. Like many Democrats, she has made abortion central to her campaign, running ads highlighting Rogers' past support for abortion restrictions.

Both candidates have national security backgrounds, with Rogers having served in the FBI and as chair of the House Intelligence Committee, and Slotkin having worked for the CIA and in the Pentagon. Slotkin has a strong fundraising record, with her campaign reporting $18 million raised in the third quarter. Republicans have also made significant investments in the state, with the Senate Leadership Fund committing $22.5 million to support Rogers. 

Ohio

Ohio Sen. Sherrod Brown is one of the most vulnerable Democrats on the ballot this year. His re-election bid against Republican nominee Bernie Moreno, a wealthy businessman and Trump ally, is considered a toss-up. Trump is expected to carry the state in the presidential race, while Brown is currently holding a four-point lead, according to a September New York Times/Siena College poll. The good news for Democrats is that Brown, a well-funded three-term Senator, is winning 10% of Trump voters, according to the same poll, and has a history of performing better than the overall Democratic statewide ticket; in 2018, he won by a little under seven points while other statewide Democratic candidates lost by roughly three to six points.

But Republicans believe their candidate can edge ahead of Brown by nationalizing the race. In one of Moreno’s recent ads, he touts his endorsement from Trump and ties Brown’s record on immigration to Harris’. Democrats, meanwhile, believe they can win Ohio by building off of Brown’s reputation as a champion for working-class voters. Brown’s campaign has capitalized on Moreno’s recent comments questioning why older women care about abortion, airing ads that highlight his own support for abortion access in a state where a ballot measure to protect reproductive rights passed with 57% support last year.

With substantial fundraising on both sides—total ad spending in Ohio surpassed $300 million—this Senate contest is ranked by AdImpact as the most expensive congressional race in the country.

Wisconsin

In Wisconsin's Senate race, Democratic incumbent Tammy Baldwin maintains a seven-point lead over Republican nominee Eric Hovde, according to a September New York Times/Siena College poll. Baldwin, the first out gay member of the Senate, has been a fixture in Wisconsin politics for more than two decades and has consistently out-fundraised Hovde, who has the resources to self-finance his campaign. 

Hovde, a banker and businessman, has attempted to frame Baldwin as out of touch with Wisconsin values, particularly on issues like border security and transgender rights. Baldwin, on the other hand, has made an effort to connect with rural voters and has received endorsements from groups like the Wisconsin Farm Bureau Federation. Polls show that Baldwin is receiving a higher share of the vote than Harris, who is leading the crucial swing state by just 1.5 points, according to 538’s polling average. 

Pennsylvania

There’s little room for error in the Keystone State, where its 19 electoral votes and contested Senate race between Democratic incumbent Bob Casey and Republican challenger Dave McCormick could play a decisive role in November. Casey's lead has fluctuated between two to nine points in various polls, though a CNN/SSRS poll in early September showed the presidential and Senate races tied in Pennsylvania.

The contest has become increasingly contentious as spending ramps up. Both the Harris and Trump campaigns have bombarded Pennsylvania with television ads, pouring $954 million across the commonwealth—more money than any other state this election cycle, according to AdImpact. The heavy presidential investment in Pennsylvania could help boost the Senate candidates, who have focused on contrasting their positions on issues like inflation and abortion. Casey's campaign has spotlighted McCormick's anti-abortion stance, while McCormick has sought to tie Casey to the Biden-Harris Administration. McCormick, a former hedge fund CEO who funded his campaign with his own money, lost a close Republican Senate primary to television doctor Mehmet Oz last cycle after he failed to win Trump’s backing. While the former President now supports him, Democrats have used some of his past attacks on McCormick in their ads to help Casey, a three-term Senator.

Arizona

In Arizona, the contest to replace retiring Sen. Kyrsten Sinema, an independent who caucuses with Democrats, has become a focal point for both parties. Democratic Rep. Ruben Gallego currently holds a substantial lead, polling 10 to 13 points ahead of Republican Kari Lake, who is a polarizing figure after her gubernatorial loss and persistent false claims of election fraud. Lake’s campaign has attempted to pivot away from her spurious claims about election integrity, focusing on issues like inflation and immigration. But Lake has been consistently polling behind Trump, who leads in Arizona by just under two points according to 538’s polling average. 

Democrats believe Gallego's efforts to position himself as a pragmatic, experienced leader with a Harvard education and combat experience in Iraq are resonating, particularly with Latino voters. He has slammed Lake for her past support for banning abortion and for continuing to falsely claim the 2022 election was stolen, while Lake has painted Gallego as a far-left radical who voted for the Inflation Reduction Act, which she is labeling the “Kamala Inflation Act” since she cast the tie-breaking vote. While the contest in Arizona doesn’t appear as close as some of the other races on this list, the state has a large portion of independent voters that will likely decide the result. An abortion-related referendum will also be on the state ballot, which could boost Gallego. 

Read More: Here’s Where Abortion Will Be on the Ballot in the 2024 Election

Nevada

Democratic Sen. Jacky Rosen's re-election campaign in Nevada is proving more secure than expected against Republican challenger Sam Brown. Recent polling indicates Rosen leading between seven and 10 points, buoyed by her incumbency and strong fundraising efforts. Brown, a West Point graduate and Army veteran who was severely burned in 2008 in Afghanistan when a roadside bomb exploded, has struggled to gain traction with Republican voters despite a compelling personal story.

Rosen has capitalized on the abortion issue, which is on the ballot in Nevada, highlighting her commitment to reproductive rights. Brown has said that he supports current state law legalizing abortion up to 24 weeks and would “close the door” on a federal abortion ban in the Senate. He and his wife even shared a personal story of her having an abortion as a young woman. (Democrats have pointed out that in a past race, Brown supported banning the procedure except in the case of a mother’s life being at risk).

Texas

Democrats are making a significant push to unseat Republican Sen. Ted Cruz in Texas, turning up the heat in what many pollsters consider a sleeper race that could upend expectations. Rep. Colin Allred, the Democratic candidate who is outraising Cruz, has gained momentum in recent months as he highlights issues related to abortion rights and border security, hoping to appeal to independents and moderates who are disenchanted with Cruz. A statewide poll by Morning Consult in September found that Allred is polling ahead of Cruz for the first time this cycle, while other polls show him trailing within a margin of error. 

If Democrats can make a real run at Texas, it would allow them more room to keep the Senate even if they lose Montana. The last time a Democrat won a Senate seat in Texas was in 1988, though Democrat Beto O’Rourke came within three points of Cruz in 2018. Democrats are hoping that Allred, a former NFL player who flipped a Dallas-area House seat and would be the state’s first Black senator if he wins, can be the one to change that.

The election has been cast by many as a referendum on Cruz, who has struggled with popularity in Texas. Allred has accused Cruz of “doing nothing to secure the border,” flipping the script on Republicans and blaming him for blocking the Senate’s bipartisan border deal earlier this year. Allred has also hit Cruz on abortion; an ad put out by his campaign and the Democratic Senatorial Campaign Committee (DSCC) featuring Kate Cox, who had to leave Texas to seek an abortion after her fetus was diagnosed with a fatal condition, and Amanda Zurawski, who sued the state after being denied an abortion despite facing complications, has received attention. “If you’re experiencing pregnancy complications in Texas, you’re in danger,” Zurawski says in the ad, “and it’s Ted Cruz and the anti-abortion extremists’ fault.” 

Meanwhile, Cruz has resurfaced comments that Allred made during the Trump Administration calling a border wall “racist,” which Allred said was taken out of context. Cruz has also targeted Allred for his support of legislation that would have banned LGBTQ discrimination in public places and his vote against a bill that would cut off federal funds for athletic programs that allow transgender athletes in women’s sports. “Boys and girls are different,” one of Cruz’s ads begins.

It remains to be seen whether Allred can capitalize on the dissatisfaction with Cruz to turn Texas blue, but his fundraising efforts so far have been striking: He brought in more than $1 million in a day twice in the third quarter, his campaign says.

Maryland

Typically a Democratic stronghold, Maryland is witnessing a surprising challenge by Republican nominee Larry Hogan, the popular two-term governor whose moderate appeal and high-profile endorsements are expected to keep this race in play for Republicans. Still, Democrat Angela Alsobrooks, the Prince George’s County Executive, holds a sizable lead for Maryland’s open Senate seat, which has been held by Democratic Sen. Ben Cardin since 2007. A recent Washington Post-University of Maryland poll shows Alsobrooks leading by 11 points, while Maryland-based pollster Patrick Gonzales had her up five points. AARP’s bipartisan polling team, however, found the Maryland Senate race tied at 46% even though Harris led the presidential race by about 30 points in the poll.

Hogan, who has a track record of bipartisanship and rejected Trump’s endorsement earlier this year, has been polling well with Democratic voters. He’s expected to perform better than Trump in the state, but most analysts are skeptical that it will be enough to counter Alsobrooks, a former prosecutor and Harris ally who would be Maryland’s first Black senator if elected. Biden won the state by 33 points in 2020. 

Florida

A potential dark horse of the 2024 cycle, Democratic hopes in Florida hinge on former Rep. Debbie Mucarsel-Powell, who served one term in the House after the 2018 blue wave and is challenging incumbent Republican Sen. Rick Scott, the former two-term governor and Trump ally. Scott maintains a solid foothold in the state, which Trump carried by three points in 2020, but is only narrowly ahead of Mucarsel-Powell in most polls. An early September poll by Emerson College showed that Scott is leading by just one point, while a Morning Consult poll published just under two weeks later had him up four points.

With Florida being a potential—but unlikely—swing state, Democrats are hoping they can rally voters around key issues like healthcare and abortion rights. For Mucarsel-Powell to win, she will likely need to appeal to disenchanted voters who may have previously supported Scott. But with Florida’s substantial population of conservative-leaning retirees, many analysts say the state remains right-of-center this election cycle. Scott has also outraised Mucarsel-Powell by $30 million (including $14 million in self-funding) to $14 million. His self-funding helped him win razor-thin gubernatorial and Senate victories in 2010, 2014, and 2018.