Celebrity heart surgeon Dr Mehmet Oz held a razor-thin lead over former hedge fund chief executive David McCormick in a Pennsylvania Republican primary race for the US Senate that was too close to call on Wednesday.
Both candidates addressed crowds late on Tuesday night saying they were confident of a victory. Dr Oz led Mr McCormick by about 2,000 votes as of Wednesday morning, with 95 per cent of the votes counted, the The New York Times reported.
Many Republicans fear Ms Barnette would be considered too conservative for general election voters.
Dr Oz's campaign has been helped by an endorsement from former president Donald Trump, whose kingmaking status within the Republican Party has been closely watched during the primary season. Mr Trump's state governor candidate, Doug Mastriano, handily won his primary, the Times projected.
If elected, Dr Oz would be the nation's first Muslim senator.
Perhaps best known as the host of The Dr Oz Show, he has fended off criticisms among conservatives about his views on abortion, guns and other issues.
Throughout his campaign, Dr Oz was also repeatedly attacked for holding dual Turkish citizenship, and he accused Mr McCormick of making "bigoted attacks". Dr Oz said he would revoke his dual citizenship if elected to the Senate.
In the weeks leading up to the primary, Mr Trump branded Mr McCormick as a liberal and part of the Washington establishment.
There is no runoff law in Pennsylvania. But the race was close enough to trigger Pennsylvania’s automatic recount law, with the separation between Dr Oz and Mr McCormick inside the 0.5% margin that triggers an order by the state’s top election official.
John Fetterman cruises to Democratic nomination win
Pennsylvania lieutenant governor John Fetterman easily won his party's primary, just days after announcing he suffered a stroke in the weekend leading up to it.
Mr Fetterman made a brief video appearance from his hospital room at the election party where his wife, Giselle, addressed the crowd.
The Democratic candidate received a defibrillator implant earlier on Tuesday. He said he cast his vote from Penn Medicine Lancaster General Hospital using an emergency absentee ballot.
President Joe Biden issued a statement celebrating Mr Fetterman's victory, saying "Democrats are united around John, who is a strong nominee, will run a tough race, and can win in November".
Agencies contributed to this report