Republicans are defending a slim Senate majority in 2026, but Democrats still have a tough fight ahead to take control of the chamber.
Democrats need a net gain of four seats to take control of the Senate in two years. And while there are 20 Republicans up for re-election in the upcoming midterms compared to 13 Democrats, many of those Republicans are running in deep-red states.
Just one GOP senator is running in a state Vice President Kamala Harris won in November, Sen. Susan Collins of Maine, while two Democrats (Georgia’s Jon Ossoff and Michigan’s Gary Peters) are up for re-election in states President-elect Donald Trump won.
This class of senators will be facing a different political environment than they did in their last races in 2020, when they were running in a presidential election year with historic turnout. And the environment could also be very different from 2014, when several of these Republicans were first elected to the Senate in a red wave. The upcoming 2026 elections could be trickier for Republicans, since the president’s party historically struggles in midterms.
Another factor that could shake up the Senate map: whether longtime lawmakers like Sen. Mitch McConnell, the outgoing GOP leader, decide to retire. McConnell, 82, has not yet said if he’ll run for another term in ruby-red Kentucky, though he has committed to serving out his current term.
As the battle for the Senate takes shape, here are the key races to watch.
Top targets
The core of the 2026 battleground map consists of the three senators up for re-election in states that backed the opposite party for president this year, making them top targets heading into the midterms.
Collins is the only GOP senator representing a state that Harris won in November. Collins has signaled that she intends to run for a sixth term, and she has been tough to beat in the past despite Maine’s blue lean.
Collins defeated former state House Speaker Sara Gideon by 9 points in 2020, even as Joe Biden won the state by 9 points, too. Democratic Gov. Janet Mills, who cannot run for that office again due to term limits, has not ruled out taking on Collins, according to the Portland Press Herald.
On the flip side are the two Democrats up for re-election in states Trump carried in November.
Peters is fresh off of two stints as head of the Democratic Senatorial Campaign Committee, and he is no stranger to tough races in Michigan. Trump carried the state by 1 point in November after losing it by nearly 3 points in 2020. That year, Peters also won a second term by nearly 2 points, defeating now-GOP Rep. John James.
Ossoff is running for a second term in Georgia, which Trump carried by 2 points this year. Ossoff won a hotly contested Senate runoff on Jan. 5, 2021, narrowly defeating then-GOP Sen. David Perdue, who has been tapped to be Trump’s ambassador to China.
Georgia GOP Gov. Brian Kemp, who cannot run for governor again due to term limits, is a potential Senate candidate. Kemp told Fox News last month that he is focused on leading the Republican Governors Association but that he tries to “keep all doors open.”
Sen. Thom Tillis, R-N.C., is expected to be another top Democratic target, running for re-election in a perennial battleground state Trump won by 3 points. Tillis has won his two Senate races by less than 2 points each.
Outgoing Democratic Gov. Roy Cooper told WSOC-TV that a Senate run is “on the table,” but he has not yet decided if he’ll jump into the race. Democratic Rep. Wiley Nickel also told Bloomberg Government he is likely to formally announce a Senate run in February, after he did not seek re-election in his redrawn district.
Primary fights
Some Republicans could face primary fights against Trump-aligned challengers, as Trump’s allies threaten to take on senators who do not support Trump’s Cabinet picks or the president-elect’s agenda.
Primary speculation is already swirling around Iowa Sen. Joni Ernst as she navigates the confirmation process for Trump’s defense secretary pick, Pete Hegseth. And Texas Attorney General Ken Paxton, also a Trump ally, has suggested he might challenge GOP Sen. John Cornyn.
One Senate Republican has already drawn a primary challenger: two-term Louisiana Sen. Bill Cassidy. He is one of three GOP senators left in the chamber who voted to convict Trump on impeachment charges after the Jan. 6, 2021, riot at the Capitol.
Louisiana state Treasurer John Fleming, a former congressman who served in the first Trump administration, launched a challenge against Cassidy earlier this month, citing that impeachment vote to argue that Cassidy “has failed the people of Louisiana.”
Cassidy’s main electoral challenge in the ruby-red state would be in a primary. And it remains to be seen whether Trump, who won Louisiana by 22 points in November, will try to take out Cassidy and boost a primary challenger.
Other battlegrounds
With Michigan, Georgia and North Carolina the only perennial battlegrounds hosting Senate races in 2026, both parties will have to reach deeper into the opposing party’s territory to try and pick up more seats.
National Republican Senatorial Committee Chairman Tim Scott, R-S.C., told Fox News that Republicans could “expand the map” by targeting New Hampshire and Virginia.
Scott also said Republicans could look at New Mexico and Minnesota “if you’re stretching,” noting Trump improved his margin in those states. Harris carried New Mexico by 6 points and Minnesota by 4 points this year.
Incoming Senate Minority Leader Chuck Schumer, D-N.Y., has yet to name a new DSCC chair, although Sen. Kirsten Gillibrand, D-N.Y., is expected to get the post, according to Axios.
But Democrats could take a look at Senate seats that they also contested in 2020, like Iowa or Texas. While Trump carried both states by around 13 points this year, he won them by single digits four years ago. Both Ernst and Cornyn won re-election in 2020 by 7 and 10 points respectively, but they could face a tougher political environment in a midterm election year.
Looming special elections
Trump’s presidency is also set to cause two resignations in the Senate, which will be filled at first by gubernatorial appointments but then by special elections in 2026.
Sen. JD Vance, R-Ohio, will leave the Senate to become Trump’s vice president, and Florida Sen. Marco Rubio has been tapped to be Trump’s secretary of state.
Ohio GOP Gov. Mike DeWine will select someone to replace Vance in the Senate, and a special election will be held in 2026 to fill the final two years of Vance’s term, with several statewide and other elected officials among the possible picks.
If Rubio is confirmed, GOP Gov. Ron DeSantis would also appoint a successor, and a 2026 special election would be held for the final two years of Rubio’s term. DeSantis wrote in a post on X in November that he had “already received strong interest from several possible candidates,” and he would likely make a decision in early January.
Both states have shifted significantly toward Republicans in recent elections, but Democrats could be eyeing recruits they think are capable of putting the states in play in what could be a more favorable Democratic year.
In Ohio, for example, Democratic Sen. Sherrod Brown has not ruled out a run for Vance’s seat after he lost re-election this year, when he ran ahead of Harris.
