Ramaswamy said his campaign would spend $4m (£3m) to air the ad across the state.

After the ad began airing, the editorial board of local Ohio news outlet the Columbus Dispatch endorsed Acton, describing the ad as “revolting and unsettling”.

The billionaire biotech entrepreneur ran against Trump for the Republican nomination in 2024. He switched gears to the Ohio governor’s race and pitched himself as a political outsider – like Trump – who wanted to develop the president’s “America First” agenda.

In his concession speech, Ramaswamy said he is “rooting” for the state, as well as Acton.

Acton is a physician and public health official who talked about her experience with homelessness as a child while campaigning for affordability.

In her acceptance speech on Tuesday, she said “the healing begins today”.

“My promise to Ohio, to those who voted for me and those who did not, is that I will work with anyone and everyone, and I always have to make life better for Ohioans,” she said.

Acton succeeds Republican Governor Mike DeWine, who is term limited.

Ohio is a swing state that voted for Trump in the 2024 election, but now Republican candidates are facing close challenges across the country.