WATCH: Roger Stone falls apart under questioning by MSNBC’s Andrea Mitchell

Roger Stone appears frequently on right-wing fringe broadcasts, where he unspools wild conspiracy theories about the president's enemies, but the longtime Republican operative fell apart under follow-up questioning by MSNBC's Andrea Mitchell.

The GOP "dirty trickster" denied reports that President Donald Trump, his longtime confidant, had grown tired of Rudy Giuliani's TV antics against special counsel Robert Mueller's probe.

"I have not heard that from credible sources around the president," Stone insisted. "I think it is fair to say that Mayor Giuliani is a very tough guy, and right now the president needs a tough leader on his legal team."

Stone issued attacks on Mueller and deputy attorney general Rod Rosenstein, but he stuttered, furiously blinked and fiddled with his earpiece after Mitchell asked him to explain why he previewed stolen emails that U.S. intelligence believe were stolen by Russian hackers.

"Coincidence," he said. "Let's go back to the previous tweet, which was crucial. I said 'the' Podestas, apostrophe 'S' -- should have been 'S,' they tell me -- the time in the barrel will come."

Mitchell wasn't distracted, and Stone continued floundering when she pointed out that Hillary Clinton's campaign chairman John Podesta's stolen emails were dumped online shortly after the "Access Hollywood" tape was revealed.

"That would be based on conjecture, supposition -- there's no evidence that would suggest that is what I was speaking to," Stone said, as he adjusted his earpiece. "I never said anything of the kind."

Mitchell asked him to explain his Aug. 4, 2016, tweet claiming to have shared dinner with WikiLeaks founder Julian Assange, and Stone claimed the email was a joke to his "neurotic" colleague Sam Nunberg.

"It's schtick, please," Stone said. "My passport, customs records, airline records, the security cameras at the Ecuadorian embassy, my hotel bill, my airline bills to Los Angeles and a receipt from Izzy's Diner on Santa Monica Boulevard would show you that I was not in London that weekend and could not have met with Assange. And to anticipate a follow-up question, no, neither by Skype or phone, either."

Stone then blamed a faulty earpiece for his brief delay before denying that he had met with Mueller and his investigators, and he cast doubt on the U.S. intelligence consensus about Russian hacking of Democratic targets during the 2016 election.

"I don't buy into the premise that Guccifer is indeed a Russian asset," he said. "I think that is unproved."

Stone claimed only MSNBC and other media outlets had concluded the hacker was a Russian operative, and he was thrown off balance when Mitchell pointed out that Mike Pompeo, Trump's former CIA director and current Secretary of State, agreed.

"The evidence, Mr. Pompeo," Stone began. "Our intelligence agencies have been politicized. This is, in my opinion, an open question. There's vigorous debate on it on the internet. Guccifer 2.0, whoever that is, is using software that is registered to a person who works at the Democratic National Committee."

"A number of counterterrorism IT experts in a great piece published by The Nation questioned whether the DNC was ever hacked," he continued, "whether the purloined information was taken out the back door through some kind of portable computer drive, so it is unproven at best. But in all honesty, it's irrelevant because my only 24-word communication with him happened six weeks after WikiLeaks has already published the story, the allegedly hacked emails, consequently, could not have colluded with him to do so -- it's chronologically impossible."

Stone then insisted the accusations against him were too stupid to be plausible.

"I made that exchange on Twitter entirely public," he said. "Who would conduct international espionage on Twitter?"