Rep. Adam SchiffAdam Bennett SchiffMystery in Mueller probe: Where’s the hacking indictment? Top Intel Dem slams Trump claim about FBI informant Sunday shows preview: Lawmakers weigh in after Texas school shooting MORE (Calif.), the top Democrat on the House Intelligence Committee, offered high praise for Sen. John McCainJohn Sidney McCainOvernight Defense: Pompeo lays out new Iran terms | Pentagon hints at more aggressive posture against Iran | House, Senate move on defense bill Senate GOP urges Trump administration to work closely with Congress on NAFTA Sarah Sanders: ‘Democrats are losing their war against women in the Trump administration’ MORE on Friday, saying the Arizona Republican's vocal criticism of President Trump marks his "finest hour."

"I think frankly this is John McCain's finest hour," Schiff said on HBO's "Real Time with Bill Maher."

"Probably his most important public service since Vietnam is what he is doing now. I wish we had more Republicans in the House, or maybe even one in the House, who is willing to follow his example."

McCain has been adamant in his calls for an independent commission to investigate Russia's efforts to meddle in the 2016 presidential election, as well as the Trump campaign's alleged ties to Moscow.

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The senior Arizona senator has also been critical of Trump's "America first" approach to foreign policy, saying earlier this month that "it's more confusion than anything else."

More recently, McCain has taken aim at the president over his decision to fire FBI Director James Comey, a decision he called disappointing. He told foreign officials on Tuesday at a meeting of the Munich Security Conference that if Trump hoped to interrupt the FBI's ongoing Russia investigation it would not work.

"I regret it, I think it’s unfortunate," McCain said. "The president does have that constitutional authority. But I can’t help but think that this is not a good thing for America."

The House Intelligence Committee is conducting its own probe into Trump and his aides' potential ties to Russia, and Schiff has been a vocal proponent of accelerating the investigation.