Mr. Gowdy and Mr. Ryan were among a small group of congressional leaders briefed on the informant late last month by top officials from the F.B.I., Justice Department and the office of the director of national intelligence. The unusual meeting came after Mr. Trump intervened on behalf of Representative Devin Nunes, Republican of California and the chairman of the Intelligence Committee, who was demanding information related to the informant.

Mr. Ryan has encouraged Mr. Gowdy, a former federal prosecutor and one of the House Republicans’ most experienced investigators, to help calm tensions between Mr. Nunes and the Justice Department. The two sides have repeatedly clashed as Mr. Nunes, a close ally of the president’s, has demanded greater and greater access to delicate case files.

Democrats emerged from the highly secretive briefing saying that they had seen “no evidence to support any allegation that the F.B.I. or any intelligence agency placed a ‘spy’ in the Trump campaign, or otherwise failed to follow appropriate procedures and protocols.” But Mr. Gowdy was the first Republican to break ranks a few days later, when he said on Fox News that the agency had acted properly.

“I think when the president finds out what happened, he is going to be not just fine, he is going to be glad that we have an F.B.I. that took seriously what they heard,” Mr. Gowdy said.

He added, “I am even more convinced that the F.B.I. did exactly what my fellow citizens would want them to do when they got the information they got, and that it has nothing to do with Donald Trump.”

People familiar with the matter have said that the informant was an American academic and veteran of Republican administrations who was to trying to glean information about what several campaign aides knew about the Russian efforts to hack into Democratic emails.

Senator Richard M. Burr, Republican of North Carolina and the chairman of the Senate Intelligence Committee, also put his support behind Mr. Gowdy’s analysis on Wednesday, after Mr. Ryan’s remarks. Mr. Burr had been silent after participating in the confidential briefing on the matter in late May.