Nigel Farage, the pro-Brexit campaigner and serial disrupter of British politics, on Monday announced plans to run as a candidate in Britain’s general election next month, dealing a new setback to the prospects of the country’s embattled prime minister, Rishi Sunak.
The surprise announcement from Mr. Farage, who represents an insurgent hard right movement, threatens to upend an election campaign by taking votes from Britain’s governing Conservative Party. In doing so, he could make it even harder for Mr. Sunak and his party to narrow a double-digit gap in the polls with the opposition Labour Party.
Divisive, charismatic and famed for his communication skills, Mr. Farage was one of the architects of Brexit, which a slim majority of Britons supported in a 2016 referendum. His earlier decision not to run in the election was thought by some analysts to have sapped momentum from Reform U.K., the successor to the Brexit Party he once led.
Mr. Farage last month said that he would not seek a parliamentary seat because he wanted to prioritize supporting Donald J. Trump’s electoral campaign in the U.S. Mr. Farage is a longtime ally of the former president and campaigned for him in 2020.
But on Monday Mr. Farage reversed his previous decision and said he would take over as leader of Reform U.K., and run for a seat in Parliament.
“I’ve changed my mind — it’s allowed you know,” he said. “I am going to stand in this election,” adding that he would run in Clacton-on-Sea, a seaside area where support for Brexit has been strong.
The announcement comes on the eve of one of the biggest events of Britain’s general election campaign so far: a televised debate between Mr. Sunak and Keir Starmer, the leader of the opposition Labour Party.
With his Conservative Party trailing badly in opinion polls, and after an accident-prone start to the general election campaign, Mr. Sunak is already under significant pressure.
The change of heart by Mr. Farage could worsen prospects for the prime minister because, according to analysts, Reform U.K. threatens to take a significant number of votes from the Conservatives.
