The math underpinning the fight for control of the Senate is pretty straightforward this cycle.

Democrats (including independents who caucus with them) hold 47 seats, while the GOP holds 53. With a Republican in the White House — and the vice president available to break any ties — Democrats need to flip a net of four seats to take back the Senate majority. 

The 2026 Senate class includes 13 seats currently held by Democrats and 22 seats held by Republicans. That should give Democrats plenty of opportunities to flip GOP seats.

But a state-by-state rundown of Senate races shows significantly more Democratic than Republican seats  “at risk.” There’s an extra dose of uncertainty this year because of the number of Senate retirements. 

Four incumbent Democrats — Richard J. Durbin of Illinois, Tina Smith of Minnesota, Jeanne Shaheen of New Hampshire and Gary Peters of Michigan — have decided not to run for another term. The races in the Granite State and in Michigan look particularly competitive at this point.

Four Republicans — Thom Tillis of North Carolina, Joni Ernst of Iowa, Tommy Tuberville of Alabama and Mitch McConnell of Kentucky — are also not seeking reelection to the Senate. A fifth Republican, Ohio’s Jon Husted, was appointed to his Senate seat and is on the ballot next year to serve out the remainder of Vice President JD Vance’s term.

Senate Democrats’ route to the majority requires them to hold all their seats up next year, including that of Georgia Sen. Jon Ossoff, among the most vulnerable incumbents. From there, the path for Democrats would necessitate them flipping the seats of Sen. Susan Collins in Maine, Husted in Ohio, Tillis in North Carolina and at least one other Republican seat.

Following former North Carolina Gov. Roy Cooper’s entry into the Senate race, Tillis’ open seat now looks vulnerable. Cooper’s likely opponent, former Republican National Committee Chairman Michael Whatley, has President Donald Trump’s complete support, but the state is very competitive. The combination of Cooper’s popularity with the normal midterm dynamic could hurt the president’s party.

In Maine, Collins has proved her ability to win swing voters, holding on to her seat when other Republican colleagues could not.

But the longer she is in office, and the longer Trump represents the Republican Party, the more difficult Collins’ task becomes — especially now that Democratic Gov. Janet Mills is considering a challenge.

Ernst’s seat in Iowa favors Republicans in a state that has moved steadily toward the GOP. Rep. Ashley Hinson is widely regarded as the early favorite for the Republican nomination to succeed Ernst, though the field in both parties is unsettled.

In Ohio, Husted is facing a challenge from Democratic former Sen. Sherrod Brown. Husted has served in multiple Ohio state offices, including the state House and the state Senate, and as secretary of state, lieutenant governor, and his current stint in the U.S. Senate. He also benefits from the state’s recent Republican drift.

But Brown is a proven vote-getter in the Buckeye State as well, having won statewide multiple times, in addition to stints in the state and U.S. House. Brown beat Republican Rep. Jim Renacci 53 percent to 47 percent in 2018 (Trump’s first midterm election), and he lost by about 3 and a half points to challenger Bernie Moreno in 2024, a presidential year that favored the GOP.

Brown has always done well among working-class populists and would likely perform better in a midterm cycle with an unpopular Republican incumbent in the White House. 

In Texas, Democrats face a long shot to win the seat held by incumbent Republican Sen. John Cornyn, who himself faces a difficult primary challenge from state Attorney General Ken Paxton.

Democrats have long thought they could make significant inroads in the Lone Star State, but so far, they have little to show for their efforts, except for then-Rep. Beto O’Rourke’s 3-point loss to incumbent Republican Sen. Ted Cruz in 2018.

Paxton is running as an uncompromising “Trump conservative” and portraying Cornyn as an “establishment” insider. Cornyn served in Senate GOP leadership for years as chair of the National Republican Senatorial Committee and as GOP whip.

Democrats might be hoping their ace in the hole for next year’s elections is the midterm dynamic. 

Trump’s job approval numbers are underwater, ranging from the upper 30s to the low 40s, and Republican turnout is likely to be lighter next year than it was in 2024, since Trump won’t be on the ballot to motivate his supporters.

The midterm elections, always challenging for the party in the White House, are even more uncertain in 2026, since the president’s party also holds the majority in the House, the Senate and the Supreme Court. Whatever happens, on whatever level, that party would bear the responsibility.