Witness in Stone Trial Says Political Operative Misrepresented Him

When Judge Amy Berman Jackson said he was “a little mumbly” and should speak up, Mr. Credico said he felt like Mumbles, a villain in the old “Dick Tracy” comic strip. “Let me know if I do it again,” he told her.

At another point, he broke into a brief, convincing impression of Senator Bernie Sanders, the Democratic presidential candidate. “We know you are a comedian, but this is serious business,” the judge chided him.

Mr. Credico described a long, rocky friendship with Mr. Stone. In 2011, at a low point in their relationship, he said, Mr. Stone posted messages on social media reporting that he had died of a drug overdose. That “caused some problems” with family members and friends, Mr. Credico said dryly.

Text messages and emails between the two men, introduced into evidence, are laced with profanity and insults. In one text, Mr. Stone referred to Mr. Credico as “Rummy,” a reference to his drinking problems. Yet they also helped each other professionally. Mr. Credico said Mr. Stone was an excellent guest on his radio show.

Although the trial only began on Tuesday, Mr. Stone’s lead defense lawyer, Bruce S. Rogow, appears to be struggling. When he announced that he was not going to cite page or exhibit numbers while questioning an F.B.I. agent, Judge Jackson instructed him to do so.

After Mr. Rogow concluded a ponderous, sometimes confusing cross-examination, the judge waited until the jurors had left the courtroom, then told him that he had “tested the patience of the jury a great deal.”

Zach Montague contributed reporting.