After their summer recess, lawmakers will return to Washington in September with a closer eye on the 2026 midterm elections.

Several senators face tough primary battles. Others are on the way out, leaving their seats open—and increasing uncertainty in battleground state elections. Others face an electorate that tends to vote against their party.

Here are five major races to watch in 2026.

1. Georgia

In the Peach State, Sen. Jon Ossoff (D-Ga.) faces an electorate that backed President Donald Trump by 2.2 percentage points in 2024.

Trump was propelled in part by extremely high turnout in Georgia’s rural counties.

While the state has strong Republican roots, Democrats have increasingly made gains in Georgia, partly driven in recent years by the explosive growth of the Atlanta metropolitan area—where voters tend to favor Democrats.

Ossoff was first elected in 2020, one of two surprise Senate wins for Democrats in Georgia—alongside Sen. Raphael Warnock (D-Ga.), who was running in a special election.

In 2022, Warnock won reelection over Republican Herschel Walker in a runoff in which Warnock took 51.4 percent of the vote to Walker’s 48.6 percent.

The political shifts in the Peach State in recent years make it difficult to predict an outcome in the 2026 race, which the Cook Political Report rates as a toss-up.

It’s unclear which candidate Republicans will back for the seat.

Rep. Buddy Carter (R-Ga.) has declared his intention to run, while other potential contenders are Reps. Mike Collins (R-Ga.) and Rick Allen (R-Ga.) and Republican state Sen. Colton Moore.

Georgia Gov. Brian Kemp, also a Republican, has said he doesn’t intend to run for the post.

2. Maine

Sen. Susan Collins, the only New England Republican left in the U.S. Senate, faces the opposite situation.

First elected to the Senate in 1996, Collins has won reelection four times even as her home state, and the Northeast as a whole, veered heavily toward the Democrats. Vice President Kamala Harris won the state by seven points in 2024.

Collins has held onto the position in part because of her regular defections from the GOP party line—particularly on social issues.

Most recently, she was a strong critic of the One Big Beautiful Bill Act and a $9.4 billion spending cuts package proposed by Trump.

One of the most electorally successful Democrats in Maine, Rep. Jared Golden (D-Maine), has declined to seek the Democratic nomination to challenge Collins in 2026.

David Costello, a former consultant who was the Democratic nominee against Sen. Angus King (I-Maine) in 2024, has announced his intention to run.

A handful of state government Democrats, including Speaker of the Maine House of Representatives Ryan Fecteau and former state Sen. Cathy Breen, have expressed interest in the nomination.

Currently, the Cook Political Report rates the race as likely Republican.

3. North Carolina

North Carolina’s Senate seat will be up for grabs after Sen. Thom Tillis (R-N.C.) decided not to seek reelection.

Tillis first joined the Senate in 2014, one of several tea party-aligned Republicans elected during the party’s sweeping wins that year.

Since Trump’s first presidency, Tillis has often been an outspoken critic. After he joined two other Republicans to vote against the One Big Beautiful Bill Act, Trump wrote on Truth Social that it was a “big mistake” and that he would back primary challengers to the North Carolina Republican.

Tillis announced his decision against running following that vote.

The primary race for the Republican nomination in the red-leaning Tar Heel State is already packed.

It features big names in GOP politics such as Republican National Committee Chairman Michael Whatley, who decided on a bid for the nomination after Trump’s daughter-in-law Lara Trump chose not to seek the post. Rep. Don Brown (R-N.C.) is also running.

Former Gov. Roy Cooper, a Democrat, is expected to seek his party’s endorsement.

The state is considered a key national battleground and the Cook Political Report rates the race a “toss-up.”

4. Michigan

Likewise, Sen. Gary Peters (D-Mich.) has announced that he’s not seeking reelection, leaving the battleground state seat open for both parties.

Alongside Pennsylvania and Wisconsin, Michigan has quickly become one of the country’s most important swing states.

In 2024, Trump won the state by 1.4 percentage points, after having lost the state by nearly 3 points in 2020. Michigan also backed the real estate mogul in 2016, contributing to his victory over former Secretary of State Hillary Clinton.

Peters has served in the Senate since his 2014 election victory, in which he won 54.6 percent of the vote. In 2020, however, that dipped to 49.9 percent, indicative of the broader decline in support for Democrats in the Rust Belt states.

Some major Democrats are already vying to replace Peters. They include Michigan state Sen. Mallory McMorrow, former speaker of the Michigan House of Representatives and current state Rep. Joe Tate, and U.S. Rep. Haley Stevens.

Former Secretary of Transportation Pete Buttigieg and Michigan Gov. Gretchen Whitmer have declined a run for the seat.

On the GOP side, the biggest contender is former Rep. Mike Rogers, who lost his 2024 Senate race to Sen. Elissa Slotkin (D-Mich.) by just 0.34 of a percentage point.

The Cook Political Report rates the race a toss-up.

5. Texas

First elected in 2002, Sen. John Cornyn (R-Texas) is hoping that his state’s voters will give him a fourth term.

Cornyn likely wouldn’t have much trouble keeping his seat in a general election, as Trump carried the state by nearly 14 percentage points in the 2024 presidential election.

But, Cornyn will need to first survive a high-profile primary challenge from Texas Attorney General Ken Paxton.

Paxton, who’s generally more aligned with Trump’s brand of politics, has criticized Cornyn from the right, setting up a battle between the more establishment wing of the state party and its conservative faction.

Paxton has specifically condemned Cornyn’s support for U.S. aid to Ukraine, his backing of offering a path to citizenship for the beneficiaries of President Barack Obama’s Deferred Action for Childhood Arrivals program, and Cornyn’s role in the passage of a gun control bill in the wake of the Uvalde school shooting in 2022.

Cornyn has accused Paxton of character flaws, and has referenced impeachment proceedings brought against him in 2023. Paxton was impeached by the state House but acquitted in the Senate trial on charges of abuse of power, state funding, and other charges related to his handling of whistleblower disclosures from his office.

Republican Rep. Wesley Hunt has also expressed interest in the race.

Although there’s limited polling, there are early warning signs for Cornyn.

A poll from One Up Insights released on June 3 found Paxton with a 22-point lead over the incumbent. On the other hand, 22 percent of voters were undecided.

A May 28 poll from Texas Southern University found Paxton with a more-modest 7-point lead, with 34 percent compared with Cornyn’s 27 percent. Hunt drew 15 percent support in the poll.