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.”