Our initial list of the Senate’s most vulnerable incumbents for the 2026 cycle is shorter than usual after three Democratic incumbents from competitive states announced that they wouldn’t seek reelection next year. 

A year and a half out from Election Day, just three senators are running for another term in states rated as “Battlegrounds” by Inside Elections with Nathan L. Gonzales. Georgia Democrat Jon Ossoff, North Carolina Republican Thom Tillis and Maine Republican Susan Collins are all gearing up for tough races and awaiting announcements on who will step up to challenge them. 

For now, this trio makes up the most vulnerable members in the chamber, although there’s plenty of time for more incumbents to get on the list as the midterm election cycle develops. Candidate recruitment throughout the rest of the year could also shake up the list. 

Democrats surely sighed with relief Monday, when Georgia Gov. Brian Kemp announced he wouldn’t run for Senate, taking Republicans’ top would-be recruit in the state off the board. Ossoff, however, remains highly vulnerable in the Peach State, which voted for Donald Trump by 2 points last year. He’s already drawn attacks from Republicans after signaling support for impeaching Trump at a town hall last month. Still, the incumbent’s campaign war chest is among the largest of senators on the ballot next year, a sign of the battle to come. 

Just behind Ossoff is Tillis, who represents a state that last elected a Democratic senator in 2008. All eyes are on whether former Gov. Roy Cooper enters the Democratic primary, which already includes former Rep. Wiley Nickel.

Collins, no stranger to tough races, lands at No. 3. She’s so far drawn a Democratic challenger in Jordan Wood, a former House chief of staff, but others could yet enter the race. Term-limited Gov. Janet Mills has said she doesn’t currently plan to run for office next year, though the Democrat could change her mind. 

Races for open seats in Michigan, where Democrat Gary Peters is retiring, and New Hampshire, where Democrat Jeanne Shaheen is stepping down, are both likely to be among the most competitive in the country this cycle and will shape the rest of the electoral map. Republicans are also hoping to force a competitive race in Minnesota, where Democrat Tina Smith is retiring. None of the three states are represented on this list, which only looks at vulnerable incumbents. 

Two Republicans from solidly red states also make the list as they are vulnerable in their primaries. Louisiana’s Bill Cassidy, who drew a censure from his state party after voting to convict Trump at his second impeachment trial, will have to win back support from his party as the state shifts to a more traditional primary system this year. And Texas’ John Cornyn faces a primary challenge from state Attorney General Ken Paxton in a race in which support from Trump could be critical. 

Both Cassidy and Cornyn could also face additional primary challengers. 

Republicans’ current 53-seat majority and relatively few pickup opportunities make for a challenging 2026 cycle for Democrats. But the party is hopeful that more opportunities will emerge as the political environment for next year’s midterms solidifies. 

Two appointed senators, Ohio’s John Husted and Florida’s Ashley Moody, will face voters for the first time as Senate incumbents. If former Sen. Sherrod Brown, who lost reelection last year, were to challenge Husted, that race could become competitive, and issues such as tariffs could play a major role in other states coming on the map.

Here are the five incumbents on our initial list of the most vulnerable senators of the 2026 election cycle:

As he gets ready for what’s likely to be an intense and enormously expensive reelection campaign, Ossoff raised an astounding $11.1 million in the first three months of the year, entering April with a similar amount banked. The first-term Democrat has emerged as the GOP’s top target of the cycle, though no high-profile challengers have declared bids so far. Georgia Gov. Brian Kemp disappointed many Republicans both at home and in Washington when he said he would not seek the seat, saying it was “not the right decision for me and my family.” But there’s no shortage of ambitious Republicans who could seek to challenge Ossoff, including Reps. Marjorie Taylor Greene, Earl L. “Buddy” Carter, Rich McCormick and Mike Collins, state Insurance Commissioner John King and Agriculture Commissioner Tyler Harper.

For Tillis, who is in his second term, navigating the Trump era has proved challenging: He has faced opposition from both Democrats and members of his own party. The North Carolina GOP censured Tillis in 2023 in part over his votes on gay rights, gun safety and immigration. And he has already drawn a handful of primary challengers, including retired furniture manufacturing executive Andy Nilsson and author Don Brown, who have accused the incumbent of being insufficiently supportive of Trump. On the Democratic  side, former Rep. Wiley Nickel is running, but many Democrats are awaiting a decision from former Gov. Roy Cooper. Tillis raised about $2.2 million in the first quarter of 2025 and ended March with $4 million banked.

The only Senate Republican representing a state carried by Kamala Harris in last year’s presidential election, Collins is no stranger to difficult races. Collins, the chair of the powerful Senate Appropriations Committee, is running for a sixth term and will once again be relying on her personal brand as a moderate in her blue-leaning state. A University of New Hampshire poll last month found 71 percent of Mainers saying she didn’t deserve to be reelected, although some polls showed her underwater ahead of her 2020 reelection too. Collins had $3.2 million in her campaign account at the end of March. 

Cassidy’s 2021 vote to convict Trump on one article of impeachment earns him a spot on this list as he seeks a third Senate term. He’s already drawn one primary challenger who’s won statewide before, Treasurer John Fleming, and other Republicans could still enter the race. Cassidy has taken steps to underscore his support for Trump, including voting to confirm Robert F. Kennedy Jr. as Health and Human Services secretary. Louisiana is set to hold a more traditional party primary this cycle, a change from previous years when all candidates competed on a single November ballot, and this could be an additional challenge for the incumbent. Even so, Cassidy is gearing up for a fight: He reported having $7.5 million in his campaign account at the close of the first quarter. 

Everything’s bigger in Texas and that includes Senate races. The intraparty slugfest between Cornyn and state Attorney General Ken Paxton promises to be both bitter and costly, and could grow more crowded if Rep. Wesley Hunt joins the race. Paxton is positioning himself as a disruptor and plans to attack Cornyn for negotiating a bipartisan update to the nation’s gun laws. Cornyn has signaled that he’ll focus on Paxton’s legal troubles: The attorney general was impeached by the Republican-controlled Texas House in 2023 on  misconduct, bribery and corruption charges, and later acquitted following a trial in the GOP-led state Senate. Trump’s endorsement could be critical in the race. Cornyn, who has the strength of the Senate GOP establishment behind him, entered April with about $5.6 million on hand, while Paxton launched his candidacy after the filing deadline. On the Democratic side, a pair of former congressmen are weighing bids: Colin Allred, who lost to Sen. Ted Cruz last year, and Cruz’s 2018 opponent, Beto O’Rourke.