WASHINGTON – There are hundreds of House and Senate lawmakers up for reelection in 2024. But just a handful of seats will determine control of Congress and give Americans the opportunity to send a message about which party they want at the wheel. 

While all eyes will be on the presidential race next year, congressional elections will also determine whether the next president can pass their agenda, or whether Washington will face further gridlock.  

In the House, Republicans are seeking to defend and expand their razor-thin majority. Meanwhile, Democrats are eying crucial battleground districts held by the GOP that President Joe Biden won in the 2020 election.

Senate Democrats are hoping to hold on to their majority as they face significant headwinds among vulnerable incumbents in solidly red states.

Here are the races to keep an eye on heading into 2024.

The Biden 17

When it comes to control of the House, much of the focus will be on the 17 Republicans representing districts Biden won in the 2020 presidential election. 

House Republicans are trying to defend their majority as they continue their impeachment inquiry into Biden, among other investigations and conservative priorities. But as Democrats seek to recapture the lower chamber, these 17 races will be central in determining who wins the House.

• Rep. David Schweikert, R-Ariz.
• Rep. Juan Ciscomani, R-Ariz.
• Rep. John Duarte, R-Calif.
• Rep. David Valadao, R-Calif.
• Rep. Mike Garcia, R-Calif.
• Rep. Young Kim, R-Calif.
• Rep. Michelle Steel, R-Calif.
• Rep. Don Bacon, R-Neb.
• Rep. Tom Kean Jr., R-N.J.
• Rep. Nick LaLota, R-N.Y.
• Rep. Anthony D’Esposito, R-N.Y.
• Rep. Mike Lawler, R-N.Y.
• Rep. Marc Molinaro, R-N.Y.
• Rep. Brandon Williams, R-N.Y.
• Rep. Lori Chavez-DeRemer, R-Ore.
• Rep. Brian Fitzpatrick, R-Pa.
• Rep. Jen Kiggans, R-Va.

Not all of these lawmakers will necessarily lose their seats, and Republicans also have their own share of pick up opportunities heading into 2024. In Michigan, Democratic Reps. Elissa Slotkin and Dan Kildee are leaving their competitive districts, opening up their seats for Republicans’ taking. Slotkin is running for the Senate, while Kildee is retiring.

Montana’s Senate race offers GOP opportunity

Republicans have high hopes of reclaiming the Senate as Democrats play defense in two critical states former President Donald Trump won in the 2020 election: Montana and Ohio. 

Sen. Jon Tester, D-Mont., is running for a fourth term and has already won three tough elections in deep-red Montana. Testers’ chances of victory rely largely on whether ultraconservative Rep. Matt Rosendale, R-Mont., steps into the GOP primary. 

Republicans in Washington are coalescing behind Tim Sheehy, an aerospace company CEO and a retired Navy SEAL, to take on Tester next year. But Rosendale, who already ran against Tester and lost in 2018, has repeatedly teased jumping into the race again. 

A competitive primary between Sheehy and Rosendale threatens to consume valuable GOP campaign resources and weaken the ultimate Republican nominee, potentially paving a way for Tester to win a fourth term. 

Will Sherrod Brown defend his seat in Ohio?

Sen. Sherrod Brown, D-Ohio, like Tester, is also running for a fourth term. In recent presidential elections, Ohio has slowly trended right, fostering a favorable environment for Republicans.

GOP lawmakers are hoping to carry forward their momentum in the state from the 2022 midterm elections. During that race, now-Sen. J.D. Vance, R-Ohio, beat back Democratic hopes of flipping the seat, which was previously held by a Republican.

Going into 2024, the GOP has a chance to unseat Brown. Unlike Montana, Washington Republicans have largely avoided wading into the Republican primary, which is contested by three candidates: businessman Bernie Moreno, state Sen. Matt Dolan and Ohio Secretary of State Frank LaRose.

Moreno has earned the endorsement of Trump and Vance. Vance in 2022 secured the GOP nomination in part because of the former president’s backing.

But Brown has brushed off the tough race, saying in an interview with the USA TODAY Network Ohio Bureau “This campaign’s no different from any other.”

“Campaigns are about whose side you’re on. The reason I win is that voters in Ohio know that I’m on their side,” he said.

Will Arizona see a historic race?

Arizona, a notorious purple swing state, could see an unprecedented three-way race in 2024. Incumbent Sen. Kyrsten Sinema, I-Ariz., has not revealed whether she plans to run for reelection. Sinema left the Democratic Party in 2022 and has frequently drawn criticism from Democrats for bucking them on contentious issues. 

Rep. Ruben Gallego, D-Ariz., is the only prominent candidate running for the Democratic nomination. On the Republican side, conservative firebrand Kari Lake, the GOP’s 2022 failed gubernatorial candidate, is running against Mark Lamb, a pro-Trump sheriff.

Sinema has pitched her still-undeclared campaign to prospective donors as built on overwhelmingly winning independent voters and siphoning more support from Republicans than Democrats, the Arizona Republic, part of the USA TODAY Network, reported.

A memo to potential supporters included a pie chart suggesting she could claim 60% to 70% of Arizona’s independent voters. Her campaign sees her taking 10% to 20% of Democratic voters and 25% to 35% of Republicans.