Republicans' primary target is 21-term U.S. Rep. Marcy Kaptur, the longest-serving woman in House history. She is facing state Rep. Derek Merrin, a Republican endorsed by former President Donald Trump, in the closely divided 9th Congressional District that includes Toledo.

Meanwhile, first-term Democrats Emilia Sykes of Akron and Greg Landsman of Cincinnati are defending pickups they made in 2022 under congressional maps newly drawn by Republicans.

Ohio's congressional map was allowed to go forward in 2022 despite being declared unconstitutionally gerrymandered to favor the GOP. The Ohio Supreme Court cleared the district boundaries to stay in place for 2024 as part of a court settlement.

9th Congressional District

Kaptur, 78, has been viewed as among the year's most vulnerable congressional incumbents, placing Ohio's 9th District in the middle of a more than $5 million campaign battle.

Her opponent, Merrin, 38, drew statewide attention last year when he failed to win the speakership and aligned a GOP faction against Republican Ohio House Speaker Jason Stephens. The ongoing infighting has spawned litigation and contributed to a historic lack of legislative action this session.

Merrin was recruited to run by U.S. House Speaker Mike Johnson and then endorsed by Trump just 18 hours before polls were set to open in a roller coaster spring primary. Johnson got involved after audio surfaced of the leading Republican in the race criticizing Trump, which raised concerns about his electability.

Kaptur's campaign criticized Merrin, a four-term state representative, for supporting stringent abortion restrictions, including criminal penalties. She painted his positions as out of step with Ohio voters, who overwhelmingly supported an abortion rights amendment in 2023. She took heat for declining an invitation from The Blade newspaper to debate Merrin, calling him a "deeply unserious politician."

1st Congressional District

Landsman, 47, a former Cincinnati City Council member, first won the district in 2022, flipping partisan control by defeating 13-term Republican Rep. Steve Chabot.

This year, he faces Republican Orlando Sonza in the 1st District in southwest Ohio. Sonza, 33, is a West Point graduate, former Army infantry officer and head of the Hamilton County veterans services office.

Landsman, who is Jewish, drew attention late in the campaign when a group of pro-Palestinian protesters set up an encampment outside his house. He decried the demonstration as harassment and said that it required him and his family members to get a police escort to enter and exit their Cincinnati home.

13th Congressional District

Sykes, 38, spent eight years in the Ohio House, including as minority leader, before her first successful bid for the 13th District in 2022. She enjoys strong name recognition in her native Akron, which her mother and father have both represented at the Ohio Statehouse.

Sykes faces Republican Kevin Coughlin, a former state representative and senator, in the closely divided district.

Sykes has campaigned on a message of unity as she sought to attract votes from Democrats, Republicans and independents and has made ample use of social media.

Coughlin, 54, has run as a moderate who would honor Ohio's recently passed abortion rights amendment. He was supported by Johnson and Ohio U.S. Rep. Jim Jordan. Trump did not endorse anyone in the race.