One of the star witnesses in the trial of political operative and longtime President Trump friend Roger Stone took the stand Thursday, starkly contradicting Stone’s under-oath testimony to Congress about efforts to learn about Democratic emails hacked by Russia.

Punctuating his testimony with jokes, dated pop-culture references and offers to do impressions, comedian and former radio host Randy Credico told jurors that — contrary to what Stone told lawmakers — he was not Stone’s secret back channel to the anti-secrecy organization WikiLeaks, which published the emails that authorities say were hacked and ultimately released to benefit Trump’s campaign.

Stone’s trial is the last case filed by special counsel Robert S. Mueller III in his investigation of Russian interference in the 2016 presidential election. Investigators had initially been exploring Stone as they examined a possible conspiracy between the Kremlin and the Trump campaign.

Roger Stone was sentenced to 40 months in prison on Feb. 20, after being convicted of lying to Congress, witness tampering and obstruction of justice. (Adriana Usero/The Washington Post)

Two days of testimony have shed new light on why investigators were keenly suspicious of the campaign, and of Stone in particular.

Prosecutors have said that phone records show Stone and Trump talked on key dates of WikiLeaks’ actions. Prosecutors also spotlighted text messages and emails from Stone and his associates that, they contend, seem to show efforts to get in touch with the group.

Mueller’s team concluded there was insufficient evidence to establish a conspiracy between the Trump campaign and Russia. Stone has pleaded not guilty to charges he made false statements to Congress and tampered with a witness: Credico.

Prosecutors alleged Stone was motivated to lie out of a desire to protect the Trump campaign from embarrassment. The lies had real impact, denying the House Intelligence Committee access to Stone’s communications, former FBI special agent Michelle Taylor testified.

On Thursday, prosecutors sought to prove to jurors that Stone had lied and obstructed — comparing documentary evidence to Stone’s recorded words to the House committee, and displaying inflammatory messages that Stone sent to Credico.

“You are a rat. A stoolie. You backstab your friends,” Stone wrote in April 2018, adding later, “I am so ready. Let’s get it on. Prepare to die. . . .”

As Credico testified, Stone, 67, stared impassively at him — at times tilting his head back, and resting his right elbow at the defense table. Credico, by contrast, joked with Judge Amy Berman Jackson, at one point offering to do an impression of Democratic presidential candidate Bernie Sanders, at another saying he was tempted to mimic Marlon Brando.

Stone, a self-professed “dirty trickster” since the 1970s, has employed a defense that takes advantage of his unsavory reputation: Don’t believe me or anyone else. Bruce S. Rogow, his attorney, has sought to get witnesses to concede that what Stone claimed about interactions with WikiLeaks did not always prove to be true.

Credico said he was often “bluffing” in his conversations with Stone, and assumed Stone was lying himself. But after the congressional testimony, Credico repeatedly told Stone that Stone had committed “perjury,” and urged him to correct the record.

Among the alleged false claims Stone made to Congress was that he had no documentary evidence of his conversations about WikiLeaks’ founder Julian Assange. Zeroing in on Credico, prosecutors sought to show that was false.

“On the day that Roger Stone testified to the committee and said his intermediary ‘was not an email guy,’ how many written communications did Roger Stone have with Randy Credico?” Assistant U.S. Attorney Jonathan Kravis asked Taylor, the former FBI agent, in court.

“Seventy-two,” she responded, citing Stone’s phone and text records.

Taylor also presented to jurors a chart of Stone’s phone conversations with Trump campaign officials from January to November 2016. The chart showed 25 calls with campaign chairman Paul Manafort; 20 with his deputy, Rick Gates; and two with Trump himself.

Credico flatly rejected another claim that Stone made to Congress: that Credico was his secret intermediary to WikiLeaks and Assange. Credico said the only time in 2016 that he spoke to Assange was in an Aug. 25 interview on his radio show.

Credico said he didn’t even try to get information on future WikiLeaks releases because, “Julian Assange is not going to tell me about future releases.” He conceded he promised to reach out to WikiLeaks on Stone’s behalf, but testified that he never did.

Prosecutors showed jurors a bevy of messages from Stone to Credico, including one from Nov. 17, 2017, about how he should respond to the congressional committee's investigation to try to bolster that case. “Stonewall it, plead the fifth, do anything to save the plan,” the text read.

Taylor testified that Stone twice in conversations with Credico invoked the character of Frank Pentangeli, a character from “The Godfather: Part II.” Stone’s attorney has said the request was to act out a scene because of Credico’s ability as an impressionist.

The scene is one in which Pentangeli is supposed to appear as a witness in a Senate hearing into the Corleone organized crime family, but sees the family’s godfather, Michael Corleone, enter the room with Pentangeli’s brother. His demeanor changes from cocky to somber.

“When he’s being questioned, Mr. Pentangeli is asked his affiliation with the Corleone family, and he says he doesn’t know anything about it,” Taylor testified.

Credico seemed to take the moment in good fun, claiming he specialized in an impression of Vito Corleone, a different Godfather character, not Frank Pentangeli.

Credico said he did not recall ever doing the bit for Stone.

As court ended for the day and the judge sent jurors out, she instructed them not to go home and watch the movie.