Mark Sanford, a former South Carolina governor, has become the latest Republican to challenge President Trump in the party’s primary contest.
“I’m here to tell you now that I am going to get in,” Mr Sanford, a long-time Trump critic, said in an interview announcing his candidacy.
He is the third person to challenge Mr Trump for the nomination. It is seen as near impossible that anyone will take the Republican mantle from the president.
No sitting president in the modern era has lost the race to be nominee for their own party, and Mr Trump remains very popular with Republicans.
The Republican National Convention, at which the nominee will be formally chosen, will take place in late August 2020 after a series of state primary elections and party caucuses.
But some state Republican parties, including in South Carolina, have decided not to hold primaries in 2020 – to clear the path for Mr Trump and save money.
Mr Sanford, 59, is expected to centre his campaign on cutting government debt and spending. “I think we need to have a conversation on what it means to be a Republican. I think that as a Republican party we have lost our way,” he told Fox News on Sunday.
“We have lost our way on debts and deficits and spending… The president has called himself the king of debt, has a familiarity and comfort level with debt that I think is ultimately leading us in the wrong direction.”