The lawmakers — all of them members of the ultraconservative House Freedom Caucus — worked closely with the White House chief of staff, Mark Meadows, whose central role in Mr. Trump’s efforts to overturn a democratic election is coming into focus as the congressional investigation into Jan. 6 gains traction.

The men were not alone in their efforts — most Republican lawmakers fell in line behind Mr. Trump’s false claims of fraud, at least rhetorically — but this circle moved well beyond words and into action. They bombarded the Justice Department with dubious claims of voting irregularities. They pressured members of state legislatures to conduct audits that would cast doubt on the election results. They plotted to disrupt the certification on Jan. 6 of Joseph R. Biden Jr.’s victory.

There was Representative Jim Jordan of Ohio, the pugnacious former wrestler who bolstered his national profile by defending Mr. Trump on cable television; Representative Andy Biggs of Arizona, whose political ascent was padded by a $10 million sweepstakes win; and Representative Paul Gosar, an Arizona dentist who trafficked in conspiracy theories, spoke at a white nationalist rally and posted an animated video that depicted him killing Representative Alexandria Ocasio-Cortez, Democrat of New York…

Congressional Republicans have fought the Jan. 6 committee’s investigation at every turn, but it is increasingly clear that Mr. Trump relied on the lawmakers to help his attempts to retain power. When Justice Department officials said they could not find evidence of widespread fraud, Mr. Trump was unconcerned: “Just say that the election was corrupt + leave the rest to me and the R. Congressmen,” he said, according to Mr. Donoghue’s notes of the call.