Election 2024: A guide to key Congressional and gubernatorial races

While the race for the White House between Kamala Harris and Donald Trump is demanding the most attention ahead of Election Day, the outcome of Congressional elections could determine the success of a Harris or Trump presidency.

All 435 seats in the U.S. House of Representatives are up for reelection this year, and Democrats are looking to upend the current 220–212 Republican majority. Meanwhile, 34 Senate seats are up for grabs, including one special election in Nebraska, as Republicans are looking to gain control in the upper chamber as Democrats hold on to a razor-thin 51–49 majority.

If Trump wins, his presidential powers and Republican party agenda could be limited by a Democratic-majority House of Representatives, while a Republican-led Senate could interfere with the policy plans of a potential Harris administration.

Voters in 11 states will also select their next governor, who will have a more direct impact on their everyday lives on major policy issues like abortion rights, taxes and immigration.

Here are some of the key Congressional and down-ballot races to watch:

Senate races to watch

Democrats, and four independents who caucus with them, currently hold a very slim majority of 51–49 in the Senate and are on the defensive in this election. If Harris wins, Democrats can afford to give up only one seat and keep their majority. If Trump wins the election, Democrats must hold onto all of their current seats in order to maintain their majority. If elected vice president, Republican Sen. JD Vance of Ohio would become the Senate’s tie-breaking vote.

Arizona: Rep. Ruben Gallego (D) vs. former TV anchor Kari Lake (R)

Why it’s important: Joe Biden flipped Arizona in the 2020 election and it’s considered to be a 2024 battleground state. The incumbent, Sen. Kyrsten Sinema (independent), opted not to run for reelection, so her seat is up for grabs.

Florida: Sen. Rick Scott (R) vs. former Rep. Debbie Mucarsel-Powell (D)

Why it's important: In a state that has consistently voted Republican in recent years, Democrats are on the offensive as Scott defends his seat in this closer-than-expected race.

Maryland: former Gov. Larry Hogan (R) vs. Prince George's County Executive Angela Alsobrooks (D)

Why it’s important: While Biden won the deep-blue state in 2020, it’s a surprisingly close race for the open Senate seat. The incumbent, Sen. Ben Cardin (D), decided not to run for reelection.

Michigan: Rep. Elissa Slotkin (D) vs. former Rep. Mike Rogers (R)

Why it's important: Michigan is considered a 2024 battleground state after Biden flipped it from red to blue in 2020. The race for the seat left open by Democratic Sen. Debbie Stabenow, who is retiring, is considered a "toss up" by Cook Political Report.

Montana: Sen. Jon Tester (D) vs. Navy SEAL veteran Tim Sheehy (R)

Why it's important: Three-term incumbent Tester finds himself defending his seat in a state that Trump won in 2020. Cook Political Report rates this race as "leaning Republican."

Nebraska: Sen. Deb Fischer (R) vs. union leader Dan Osborn (independent)

Why it's important: While Trump won the state in 2020, incumbent Fischer finds herself in a tight race with Osborn.

Nevada: Sen. Jacky Rosen (D) vs. Army veteran Sam Brown (R)

Why it’s important: In 2020, Biden won Nevada. In 2022, the governor’s office flipped from Democrat to Republican. Rosen is defending her seat as the incumbent.

Ohio: Sen. Sherrod Brown (D) vs. businessman Bernie Moreno (R)

Why it's important: Brown is defending his seat as the incumbent in a state that Trump won in 2020. Cook Political Report rates this race as a "toss up."

Pennsylvania: Sen. Bob Casey (D) vs. businessman Dave McCormick (R)

Why it's important: Casey is defending his seat in the 2024 battleground state that Biden flipped in 2020. Cook Political Report rates this race as a "toss up."

Texas: Sen. Ted Cruz (R) vs. Rep. Colin Allred (D)

Why it's important: The increasingly tight race is a rare instance where a Democrat is on the offensive in a deep red state that Trump won in 2020.

Wisconsin: Sen. Tammy Baldwin (D) vs. businessman Eric Hovde (R)

Why it's important: In a 2024 battleground state that Biden flipped in 2020, Cook Political Report rates this race as a "toss up."

House races to watch

All 435 seats in the House are up for reelection on Nov. 5. Republicans hold a slim majority with 220 seats, while Democrats hold 212 seats. Three seats are vacant: Wisconsin’s 8th District is expected to remain Republican after GOP Rep. Mike Gallagher resigned from Congress. New Jersey’s 9th and Texas’s 18th districts are expected to remain Democrat following the 2024 deaths of Democratic Reps. Bill Pascrell and Sheila Jackson Lee.

If that happens, Democrats would need to win four more seats to gain a majority in the House. Democrats have the opportunity to flip 19 Republican-held seats that Biden won in 2020. Of those 19, these are the nine listed as "toss ups" by the Cook Political Report.

Republican-held 'toss-ups'

Arizona

1st District: Rep. David Schweikert (R) vs. Amish Shah (D)

6th District: Juan Ciscomani (R) vs. Kirsten Engel (D)

California

13th District: John Duarte (R) vs. Adam Gray (D)

22nd District: David Valadao (R) vs. Rudy Salas (D)

27th District: Mike Garcia (R) vs. George Whitesides (D)

45th District: Michelle Steel (R) vs. Derek Tran (D)

New York

4th District: Anthony D'Esposito (R) vs. Laura Gillen (D)

19th District: Marc Molinaro (R) vs. Josh Riley (D)

Oregon

5th District: Lori Chavez-DeRemer (R) vs. Janelle Bynum (D)

With Republicans on the defensive in the House, there are eight Democratic-held districts that Trump won in 2020 that the GOP could flip. Out of the eight, these are the four highly competitive races listed as “toss up” by the Cook Political Report:

Democratic-held 'toss-ups'

Alaska

At-Large District: Mary Peltola (D) vs. Eric Hafner (D) vs. Nicholas Begich (R) vs. John Howe (Alaskan Independence Party)

Maine

2nd District: Jared Golden (D) vs. Austin Theriault (R)

Pennsylvania

8th District: Matt Cartwright (D) vs. Rob Bresnahan Jr. (R)

Washington

3rd District: Marie Gluesenkamp Perez (D) vs. Joe Kent (R)

Gubernatorial races to watch

Eleven gubernatorial races are on the 2024 ballot. Eight of these races have open seats to fill. Of those, the Cook Political Report has Delaware voting solidly for the Democratic candidate, while Missouri, Montana, North Dakota, Utah, Vermont and West Virginia are likely to vote solidly Republican. The following gubernatorial races are the ones that are considered competitive.

'Toss-up'

New Hampshire: Joyce Craig (D) vs. Kelly Ayotte (R)

GOP Gov. Chris Sununu is not running for reelection

'Likely' Democrat

North Carolina: Josh Stein (D) vs. Mark Robinson (R)

Democratic Gov. Roy Cooper cannot run again due to term limits.

Washington: Bob Ferguson (D) vs. Dave Reichert (R)

Democratic Gov. Jay Inslee is not seeking a fourth term.

'Likely' Republican

Indiana: Jennifer McCormick (D) vs. Mike Braun (R)

Republican Gov. Eric Holcomb can’t run for reelection due to term limits. Cook lists this as “likely” Republican.