As a key witness testified inside the Manhattan criminal courthouse on Tuesday morning, an increasingly familiar scene unfolded outside, as another in a parade of well-known visitors — this time Mike Johnson, the speaker of the House — stepped up to a microphone.

“This is a man who is clearly on a mission for personal revenge,” Mr. Johnson said, attacking the man on the stand, Michael D. Cohen, the former fixer to Donald J. Trump. “He is someone who has a history of perjury. No one should believe a word he says in there.”

Mr. Johnson’s attacks on Mr. Trump’s behalf did what the former president himself could not, bound as he is by a gag order during his trial on felony charges of falsifying business records. In recent days, Trump allies have stepped up one after another as his proxies, although Mr. Trump used a different term.

“I do have a lot of surrogates,” he said in remarks before trial proceedings began on Tuesday, “and they are speaking very beautifully.”

The proud observation appears to reflect a game plan. And the surrogates, however awkwardly, have risked their public profiles to defend a man accused of hiding hush-money payments to a porn star.

Mr. Johnson, whose persona back home in Louisiana is defined by family and faith, concluded his brief remarks without taking questions.