AFTON, Va. — Denver Riggleman stood virtually alone.
It was Oct. 2, on the floor of the House of Representatives, and he rose as one of only two Republicans in the chamber to speak in favor of a resolution denouncing QAnon. Mr. Riggleman, a freshman congressman from Virginia, had his own personal experiences with fringe ideas, both as a target of them and as a curious observer of the power they hold over true believers. He saw a dangerous movement becoming more intertwined with his party, and worried that it was only growing thanks to words of encouragement from President Donald J. Trump.
“Will we stand up and condemn a dangerous, dehumanizing and convoluted conspiracy theory that the F.B.I. has assessed with high confidence is very likely to motivate some domestic extremists?” asked Mr. Riggleman, a former Air Force intelligence officer. “We should not be playing with fire.”
Six months later, conspiracy theories like QAnon remain a threat that most Republicans would rather ignore than confront, and Mr. Riggleman is out of office. But he is ever more determined to try to expose disinformation from the far right that is swaying legions in the Republican base to believe in a false reality.
Mr. Riggleman is a living example of the political price of falling out of lock step with the hard right. He lost a G.O.P. primary race last June after he officiated at the wedding of a gay couple. And once he started calling out QAnon, whose followers believe that a satanic network of child molesters runs the Democratic Party, he received death threats and was attacked as a traitor, including by members of his own family.
investigations into how extremists have used propaganda and faked information to sow division over some of the most contentious issues of the day, like the coronavirus pandemic and police violence.
Their reports have also given lawmakers a better understanding of the QAnon belief system and other radical ideologies that helped fuel the riot at the Capitol on Jan. 6.
Mr. Riggleman said he had written one report about the involvement of far-right militants and white supremacist groups in the attack specifically at the request of a Republican member who needed help convincing colleagues that far-left groups were not the culprits.
Getting lawmakers to see radical movements like QAnon as a threat has been difficult. Joel Finkelstein, the director of the Network Contagion Research Institute, said that in June, when the group tried to sound the alarm on QAnon to members of Congress, Mr. Riggleman was the only one who responded with a sense of urgency and agreed to help.
58 percent of Trump voters wrongly believed the storming of the Capitol was mostly inspired by far-left radicals associated with antifa and involved only a few Trump supporters.
“There was a troika of us who said, ‘This is going to a bad place,’” said Paul Mitchell, who represented Michigan in the House for two terms before retiring early this year in frustration. He said he had watched as members dismissed Mr. Riggleman, despite his experience in intelligence. “There weren’t many people who gave a damn what your expertise was,” Mr. Mitchell said. “It was inconsequential compared to the talking points.”