Former Rep. John Dingell (D-Mich.) appeared to mock Sen. John McCain John Sidney McCainAnalysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE (R-Ariz.) on Thursday, after the senior Arizona senator peppered FBI Director James Comey with a rambling line of questions during a Senate Intelligence Committee hearing.

"Naps are important. When in doubt, take a nap," the 90-year-old, who retired from the House in 2015, wrote on Twitter.

Naps are important. When in doubt, take a nap. — John Dingell (@JohnDingell) June 8, 2017

McCain delivered a broad and confusing line of questions at the end of the Comey hearing that appeared, at times, to conflate the FBI's ongoing investigation into Russian election meddling with the now-closed probe into Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE's use of a private email server.

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“The American people have a whole lot of questions out there, particularly since you just emphasized the role that Russia played, and obviously she was a candidate for president at the time, so she was clearly involved in this whole situation where, fake news — as you just described it, is a big deal — took place,” McCain said.

"You reached the conclusion that there was no reason to bring charges against Secretary Clinton, so you reached a conclusion," McCain later said to Comey.

"In the case of ... President Trump, you have an ongoing investigation. So you got one candidate who you're done with and another candidate that you have a long way to go. Is that correct?"

Comey, who at one point told McCain he was confused by the questioning, explained that the FBI had not yet reached a conclusion in its Russia investigation, but that the Clinton probe had been completed for nearly a year.

"I don't know how far the FBI has to go, but yes. The Clinton email investigation was completed," Comey replied. "The investigation of Russia's efforts in connection with the election and whether there was any coordination and, if so, with whom, between Russia and the campaign was ongoing when I left."

Neither Clinton nor her presidential campaign is believed to be the subject of the ongoing investigation into Russian influence in the 2016 election. Comey announced last summer that the FBI had closed its probe into her email server use without recommending charges against the former secretary of State.

McCain has, in the past, been among the Republican lawmakers most adamant in demands to establish an independent commission to investigate Russian election meddling and was highly critical of President Trump's abrupt decision last month to fire Comey.