Voters in Ohio on Tuesday are selecting candidates ahead of November’s midterm elections. The state is expected to play a major role in deciding whether Donald Trump’s fellow Republicans maintain control of Congress for the final two years of his term.

The race with the highest national profile is Ohio’s Senate special election, in which Sherrod Brown, a Democrat, is vying to unseat the Republican incumbent, Jon Husted, and return to the chamber after failing to win re-election in 2024. The winner will serve the final two years of the term JD Vance won in 2022, before he became vice-president last year.

Republicans in north-west Ohio will also choose their party’s nominee to take on Democratic representative Marcy Kaptur, the longest-serving woman in congressional history whose district centered on Toledo has grown increasingly conservative under new maps a state redistricting commission approved last year.

Elsewhere on the ballot, Ohioans will select candidates to replace the Republican governor, Mike DeWine, who cannot run again because of term limits. Biotech entrepreneur and former presidential candidate Vivek Ramaswamy is the Republicans’ frontrunner, and former state health department director Amy Acton the leading Democrat.

Once a swing state that decided the 2004 presidential election for Republican George W Bush before Democrat Barack Obama carried it in both his election victories, Ohio has become increasingly Republican since Trump’s ascension as the leader of the Republicans.

In 2024, the president won it by 12 percentage points, the same year that Brown, a three-term senator who has cast himself as a crusader for the midwestern state’s downtrodden working-class voters, lost his bid for a fourth term to Republican Bernie Moreno, whose victory helped put the GOP in control of the Senate.

But with Trump’s approval ratings underwater, particularly on electorally potent issues such as handling of the economy and prices, Democrats believe they may have a shot at getting Brown back into office, and re-election vulnerable lawmakers to the House of Representatives in a state where Republicans are seen as sure to win at least 10 of its 15 seats.

Both the former senator and Husted are expected to win their primaries, as is Acton. Trump and the state Republican party have endorsed Ramaswamy, who is being challenged from his right by Casey Putsch, an internet personality and auto racing engineer.

The most contested primary in the state is expected to be among the Republicans vying to unseat Kaptur, who is considered one of the most vulnerable Democrats in the country.

Republican candidates in her ninth congress district include former state house representative Derek Merrin, who lost to Kaptur in 2024 by less than 2,400 votes; Madison Sheahan, a former deputy director of US Immigration and Customs Enforcement; and Josh Williams, a state house representative.

Winners in the primaries will advance to the 3 November midterms, in which voters nationwide will elect all 435 House members, as well as 33 senators.