Democrat Amy Acton has defeated Republican Vivek Ramaswamy to win the Ohio governorship in a bitterly contested race, according to CBS News projections.
With this victory, Acton becomes the first Democrat and the first ever woman to win the Ohio governor's race in two decades.
Ohio, a key battleground for much of the 2000s, has voted for Republican Donald Trump in the last three presidential elections, including by 11 points in 2024.
But the gubernatorial race, where voter frustration over the economy and the cost of living was the central theme, took an unexpected turn after the Ramaswamy campaign released a deeply personal attack ad featuring Acton's estranged mother.
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In the ad, Acton's mother Donna Arthur said her daughter "lied her entire life". It did not mention that Arthur's husband was charged with raping Acton when she was a child.
The controversial ad loomed over the last weeks of the race. It was criticised by former South Carolina Governor Republican Nikki Haley, while Ohio's current Republican Governor Mike DeWine called it "deeply troubling".
However, some defended it, including President Trump and Vice-President Vance.
Trump described it as "powerful" and encouraged Ramaswamy to keep it running, while Vance, the state's former Senator, said he would like fellow Republicans to stop "whining" about the ad and that he was "a little bit disgusted" by criticism from members of his own party.
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.
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