Democrats’ hopes of securing control of the Senate next year begin with defending a freshman from a Southern swing state that Donald Trump narrowly carried in 2024. And Republican efforts to maintain their Senate majority center on a longtime incumbent who has managed to hang on despite representing a state that leans blue. A year out from Election Day, Georgia’s Jon Ossoff, a Democrat seeking his second term, and Maine’s Susan Collins, a Republican seeking her sixth, top our list of the most vulnerable senators of 2026. Several other incumbents — including Republicans John Cornyn of Texas and Bill Cassidy of Louisiana and Democrat Edward J. Markey of Massachusetts — also make our list. But their biggest challenge is likely to come in the primary from a member of their own party. The ranking is based on extensive conversations with campaign insiders, party officials and independent election analysts, as well as candidates’ fundraising and race ratings by Inside Elections with Nathan L. Gonzales. [Related: The 10 most vulnerable House members, a year out from 2026 elections] CQ Roll Call typically focuses on the 10 most endangered members in each chamber, but our latest Senate list features only six. Because our list focuses on incumbents, it doesn’t take into account open-seat races, whose outcomes will also determine the balance of power in the Senate. Three Democratic incumbents from competitive states — Michigan’s Gary Peters, New Hampshire’s Jeanne Shaheen and Minnesota’s Tina Smith — as well as Republicans Thom Tillis of North Carolina and Joni Ernst of Iowa all announced their retirements, leaving behind competitive seats. Democrats need a net pickup of four seats to win control of the chamber next year. Speaking before Tuesday’s off-year elections, Democratic National Committee Chair Ken Martin admitted that would be a “pretty steep” hill to climb. But sweeping Democratic wins across the country Tuesday injected some optimism into the minority party, with Senate Minority Leader Charles E. Schumer and Democratic Senatorial Campaign Committee Chair Kirsten Gillibrand, both of New York, saying the results “make clear that Republicans’ Senate majority is at risk.” Democrats harbor long-shot hopes of expanding their path to the Senate majority through red-state races that could become competitive under the right conditions. In Alaska, for instance, Democrats are already criticizing two-term Sen. Dan Sullivan for his votes in favor of legislation that included cuts to Medicaid. Former Rep. Mary Peltola, the last Democrat elected statewide, would be a strong opponent, but she has not yet announced her 2026 plans. And Nebraska’s Pete Ricketts is fighting off a challenge from independent Dan Osborn. In 2024, Osborn, a former labor leader, came within 7 points of defeating the state’s senior senator, Republican Deb Fischer. But Ricketts, a popular former governor, is seen as a stronger contender against Osborn. As the only Senate Democrat on this list from a state that Trump won in 2024, Ossoff has had to navigate the political complexities of a purple state. But this is his first test since his victory over former Sen. David Perdue in a runoff election in early 2021 helped hand Democrats control of the Senate. This year, Ossoff faces a fractured Republican field: Two congressmen, Mike Collins and Earl L. “Buddy” Carter, are running, along with former University of Tennessee football coach Derek Dooley, a political newcomer who has the backing of Gov. Brian Kemp. Despite the GOP divisions, Republicans are confident the party will coalesce behind the winner of the May primary. Ossoff, meanwhile, has a big fundraising advantage over his potential rivals. He raised $12.1 million between July and September and ended the third quarter with $21.4 million in the bank. Democrats were also encouraged by Tuesday’s election results, which saw a pair of Democrats flip two seats on the state’s Public Service Commission. Maine is unsurprisingly shaping up to host another marquee Senate race next year. Collins, the lone Republican senator representing a state won by Kamala Harris last year, has yet to officially announce her campaign for a sixth term. But the Democratic primary to take her on has heated up, with Gov. Janet Mills and oyster farmer Graham Platner locked in a battle that highlights the generational and ideological differences within the party. Platner, who raised $3.2 million in the first six weeks of his campaign, has been dogged by recent negative headlines over unsavory past social media posts and a problematic tattoo. But a University of New Hampshire survey from last month showed him with a double-digit lead over Mills. Also running is former congressional aide Jordan Wood, who's raised $3.1 million since joining the race in April. To hang on as New England’s only Republican in the Senate, Collins will have to overcome low favorability ratings (which she’s done before) and fend off Democratic attacks over health care costs and the fall of Roe v. Wade, which occurred after her last reelection. She ended September with $6.7 million banked. For months, Cornyn has been fighting for his political future against firebrand primary challenger Ken Paxton, the state attorney general. Now, the senator faces a battle on a new front, with GOP Rep. Wesley Hunt joining the field. Cornyn has Senate GOP leaders behind him, and a pro-Cornyn super PAC is already running ads supporting his campaign. That spending has boosted Cornyn's poll numbers: An October survey by the University of Houston and Texas Southern University found him and Paxton effectively tied, with Hunt in third place. Cornyn reported raising $910,000 last quarter through his main reelection committee and about $2.4 million through his joint fundraising accounts. Paxton raised $1.3 million in that same span, while Hunt netted $366,000 for his House account. On the Democratic side, state Rep. James Talarico has proved to be a fundraising juggernaut, bringing in $6.2 million in his first three weeks. Former Rep. Colin Allred, who lost to Sen. Ted Cruz by 8 points last year, raised about $4.1 million for his second Senate bid. In conservative Louisiana, Cassidy would only be vulnerable in the primary. He started October with $9.5 million in the bank, giving him a massive money edge over his GOP opponents: state Treasurer John Fleming, state Rep. Julie Emerson, state Sen. Blake Miguez, Public Service Commissioner Eric Skrmetta and St. Tammany Parish Councilwoman Kathy Seiden. But he’s on our list because he’s one of just three Republican senators still in office who voted to convict Trump at his post-Jan. 6 impeachment trial. Cassidy’s rivals have already attacked him over his vote, as they angle for Trump’s endorsement. But Cassidy supporters say he has worked to rebuild his relationship with the president. The senator has been invited to the White House more than a dozen times this year and has nominated Trump for the Nobel Peace Prize. In September, Trump sent Cassidy a birthday note thanking him for his “continued friendship and enduring commitment to our cherished American values.” Husted was Ohio’s lieutenant governor when Gov. Mike DeWine appointed him earlier this year to fill the seat left open after Republican JD Vance became vice president. A close ally of DeWine’s, Husted enjoys a clear path to the GOP nomination, unlike in recent cycles, when Vance and Bernie Moreno, now Ohio’s senior senator, each faced contentious primaries. But the special election to fill the remaining two years of Vance’s term has drawn a familiar Democrat: former Sen. Sherrod Brown, who lost his seat to Moreno in 2024. In red-leaning Ohio, Brown, the gravel-voiced populist with historical ties to the labor movement, is likely the only person who could make the race competitive, but even his supporters concede it will require a lot of money, and a bit of luck. Democrats say the impacts of Trump’s tariff policy will weigh heavily on the minds of voters, but it won’t be easy overcoming Ohio’s reliably Republican underpinnings. Brown, long a skilled fundraiser, reported total receipts of $7 million in the first six weeks since launching his bid. Husted had about $5 million in the bank at the end of September. Markey, who is 79 and the longest-serving Democrat in Congress, is facing an intraparty challenge from Rep. Seth Moulton, 47, who has framed the race as a generational battle for the future of the Democratic Party. Markey has been here before: In 2020, he handily beat back a challenge from another Democratic House member, Joseph P. Kennedy III. Markey has also built strong ties with younger progressives, including New York Rep. Alexandria Ocasio-Cortez. A new University of Massachusetts Amherst/WCVB poll found Markey leading Moulton by 20 points. The field could grow: Politico reported Tuesday that Rep. Ayanna S. Pressley is weighing a Senate run. Whoever emerges from the Democratic primary would be heavily favored in the general election. The Bay State hasn’t elected a Republican to the Senate since 2010, when Scott P. Brown notched a surprise special election win to succeed the late Democratic Sen. Edward M. Kennedy. Brown is running for Senate in New Hampshire this cycle.
