Yesterday was the public impeachment debut of Representative Jim Jordan, a conservative favorite who has become one of Mr. Trump’s loudest advocates on cable news and in congressional hearings. I asked my colleague Sheryl Gay Stolberg, who is working on a profile of Mr. Jordan, about him.

Sheryl, why is Jim Jordan effective in the eyes of Republicans?

He defends Mr. Trump at all costs. It’s very simple. He did what Republicans needed him to do yesterday, which was raise doubts about the witnesses by saying they were hearing things secondhand. He tried to poke a few holes in their testimony.

And he did that when he elicited an admission out of Mr. Taylor, when he said that in three face-to-face meetings with Ukraine’s president, the topic of military aid hadn’t come up. That’s something that Republicans have been seizing on since.

He talks so quickly. In a five-minute video he posted of himself defending Mr. Trump at the hearing, he asked no questions.