Produced by ‘The Ezra Klein Show’ Over the course of Donald Trump’s presidency, the far-right fringe became a surprisingly visible and influential force in American politics. Eruptions of extremist violence — including the Unite the Right rally in Charlottesville, Va., in 2017 and the Jan. 6 Capitol insurrection — have made militant groups like the Proud Boys and conspiracy theories like QAnon into household names. On his popular cable news show, Tucker Carlson recently name-checked the “great replacement” conspiracy theory . And in a recent survey , nearly a third of Republicans agreed with the statement that “true American patriots...