Nigel Farage, a supporter of former President Donald J. Trump, a driving force behind Brexit and Britain’s best known political disrupter, was elected to Parliament for the first time.

The new insurgent party he leads — Reform U.K. — was projected in the national exit poll to have captured four seats, more than many analysts had predicted, in an electoral system that typically punishes small parties. His party has been buoyed by an anti-immigration platform.

Mr. Farage won by a large margin in Clacton, a faded seaside town, where pre-election opinion surveys had suggested he had a strong chance of winning. He had tried and failed seven times before to be elected to Parliament.

“The establishment are terrified, the Conservatives are terrified,” Mr. Farage declared gleefully in a speech last month, referring to the governing party. Britain was “a broken nation,” he added, attacking targets ranging from asylum seekers to the BBC.

A polarizing, pugilistic figure and a highly skilled communicator, Mr. Farage, 60, helped the Conservatives to a landslide victory in the last general election by not running candidates from his Brexit Party in many key areas.

This election, his plan was different: to destroy the Tories by poaching much of their vote, then replace — or take over — the party’s remnants. Early in the campaign, after a journalist asked if he wanted to merge his upstart party with the Conservatives, he replied: “More like a takeover, dear boy.”

Reform U.K. has come under fierce criticism in recent weeks after a number of its candidates were found to have made inflammatory statements. One said that Britain should have remained neutral in the fight against the Nazis; another used antisemitic tropes by claiming that Jewish groups were “agitating for the mass import into England of Muslims.”

The party has blamed some of its problems on growing pains, has dropped some candidates and has threatened to take legal action against a private company it paid to vet candidates.

Last week, an undercover investigation by Britain’s Channel 4 News secretly filmed Reform campaigners in Clacton using racist and homophobic language, with one using a slur to describe the prime minister, Rishi Sunak.

But for two decades he has shaped Britain’s political conversation, driving the Brexit cause, outflanking the Tories and pushing them further right.

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