During former FBI director James Comey's congressional testimony on Russian interference in the 2016 election on June 8, Sen. John McCain (R-Ariz.) entered into a lengthy and confusing comparison of the investigation into Hillary Clinton's emails and the Russia investigation. (Reuters)

This post has been updated with Sen. McCain's statement.

Sen. John McCain (R-Ariz.) was the last senator to question former FBI director James B. Comey at Thursday's Senate Intelligence Committee hearing. Nearing the end of more than 2½ hours of questioning, McCain focused his line on two FBI inquiries: the 2016 investigation of Hillary Clinton's use of a private email server as secretary of state and the 2017 investigation of Russian interference in the presidential election.

But several of his questions confused viewers, and seemingly Comey himself, and he occasionally was incoherent. He referred to “President Comey,” and at times looked confused and frustrated with Comey's answers. Viewers clearly thought it was notable; Twitter announced it was the most-tweeted moment of the hearing.

“In the case of Hillary Clinton, you made the statement that there wasn't sufficient evidence to bring a suit against her, although it had been very careless in their behavior, but you did reach a conclusion in that case that it was not necessary to further pursue her,” McCain's line of questioning began. “Yet at the same time, in the case of Mr. [Trump], you said that there was not enough information to make a conclusion. Tell me the difference between your conclusion as far as former secretary Clinton is concerned, and Mr. Trump.”

Comey answered that the Clinton email investigation was a completed, closed investigation at the time he announced in July that “no reasonable prosecutor” would bring a case against her, while the Russia investigation is still underway and could be for some time.

But McCain wasn't satisfied. He seemed to be arguing that Comey exonerated Clinton, in a sense, but left an investigation looming over President Trump, setting a double standard.

Comey again tried to explain that he discussed the findings of the Clinton investigation only after it was completed.

“That investigation was going on. This investigation was going on. You reached separate conclusions,” McCain said. Comey explained, for the third time, that the Clinton investigation was about an email server and was concluded in July.

That's when it got really weird.

Sen. John McCain (R-Ariz.) asked former FBI director James Comey a series of questions at a Senate Intelligence Hearing, but appeared to be confused about FBI investigations, on June 8 at the Capitol. (Reuters)

“You're gonna have to help me out here,” McCain said. Comey replied that he was confused. In the video above, you can watch the entire exchange. But it boiled down to one point.

“I think it's hard to reconcile, in one case you reach a complete conclusion, and on the other side you have not,” McCain said. “I think that's a double standard there, to tell you the truth.”

Well, of course. The Clinton email investigation ended more than 11 months ago, while the Russia investigation continues. It was a bizarre argument from McCain, who appeared annoyed with Comey. Was he arguing that Comey should publicly exonerate Trump before the Russia investigation is finished? Was he arguing that Comey didn't investigate Clinton vigorously enough? Was he arguing that the FBI applied different standards to the two candidates?

It's hard to say, but McCain seemed to be trying to blunt the effect of Comey's testimony about Trump.

That's made all the more odd by the fact that, since Election Day (and even going back to the 2016 campaign), McCain has been one of the Senate Republicans most critical of Trump and his administration.

Sen. John McCain (R-Ariz.) has repeatedly come under attack from President Trump. Here are just a few of their rocky moments. (Peter Stevenson/The Washington Post)

McCain later released a statement, joking that “maybe going forward I shouldn’t stay up late watching the Diamondbacks night games.”

The rest of the statement reads:

What I was trying to get at was whether Mr. Comey believes that any of his interactions with the President rise to the level of obstruction of justice. In the case of Secretary Clinton’s emails, Mr. Comey was willing to step beyond his role as an investigator and state his belief about what ‘no reasonable prosecutor’ would conclude about the evidence. I wanted Mr. Comey to apply the same approach to the key question surrounding his interactions with President Trump — whether or not the President’s conduct constitutes obstruction of justice. While I missed an opportunity in today’s hearing, I still believe this question is important, and I intend to submit it in writing to Mr. Comey for the record.