In Pennsylvania, they would gather just a few blocks from the capitol, in the offices of Quantum Communications, a political consulting firm run by Trump elector Charlie Gerow (Mr. Gerow and fellow Trump elector Lou Barletta would later run unsuccessfully for the 2022 GOP nomination for governor).

It was a cold, snowy morning as Mr. DeMarco walked to his car and made the nearly four-hour drive to Harrisburg.

“I didn’t want to go,” Mr. DeMarco said.

He’d already angered many in his party by disputing the conspiracy theories and outright falsehoods about a stolen election that were being peddled by Mr. Trump and his allies. Mr. DeMarco, an Allegheny County councilman and member of the county Elections Board, had heard the complaints, but he’d also seen the evidence.

“I had to come out and say I saw no widespread fraud,” Mr. DeMarco said.

After pulling up to Mr. Gerow’s office on State Street, Mr. DeMarco sat in his car for awhile, the stately green dome of the Pennsylvania Capitol looming just to the northeast. When the meeting’s 10:45 a.m. start time rolled around, he went inside, exchanged pleasantries with a few people, signed his name on the sheet of electors, grabbed one of the sandwich rolls that had been laid out for the group, and walked back outside.

“And I got back into my car and went home.”