Nigel Farage’s Anti-Immigration Party Has Big Plans. Can It See Them Through?

A week ago, he was the keynote speaker at a glitzy Chicago dinner for the Heartland Institute, a conservative think tank with a history of denying climate science, where the top tables went for $50,000.

On Friday, it was back to the day job for Nigel Farage, the veteran political disrupter, ally of Donald J. Trump and hard right, anti-immigrant activist whose ascent has alarmed both of Britain’s main political parties.

In a cavernous exhibition center in Birmingham, in England’s West Midlands, Mr. Farage is set to address supporters of his upstart party, Reform U.K., at its first annual conference since its success in Britain’s July general election. He is expected to lay out a plan to professionalize the party and build support ahead of local elections next year.

His ambitions are clear. But the jet-setting lifestyle of Mr. Farage, 60, whose visit to Chicago was his third recent trip to the United States, underscores the question hanging over Reform U.K.: Does its leader have the ability and appetite to build the fledgling party into a credible political force?

Mr. Farage, a polarizing, pugnacious figure, is one of Britain’s most effective communicators and had an outsized impact on its politics for two decades before finally being elected to Britain’s Parliament in July. A ferocious critic of the European Union, he championed Brexit and helped pressure Prime Minister David Cameron to hold the 2016 referendum.

“A fairly strong case can be made that Nigel Farage has been the most important political figure in all the elections of the last decade,” said Robert Ford, a professor of political science at the University of Manchester.