Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeLindsey Graham basks in the impeachment spotlight Kelly, McSally virtually tied in Arizona Senate race: poll The Hill's 12:30 Report — Presented by Nareit — White House cheers Republicans for storming impeachment hearing MORE (R-Ariz.) used his formal goodbye speech on Thursday to tout the importance of upholding U.S. institutions and warned that the country's current political climate "is not healthy."

"I believe that we all know well that this is not a normal time, that the threats to our democracy from within and without are real, and none of us can say with confidence how the situation that we now find ourselves in will turn out," Flake said during his floor speech.

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He added that "to say that our politics is not healthy is something of an understatement."

Flake, who is retiring in January, has emerged as one of the President TrumpDonald John TrumpSenate gears up for battle over witnesses in impeachment trial Vulnerable Democrats tout legislative wins, not impeachment Trump appears to set personal record for tweets in a day MORE's most vocal GOP critics dating back to the 2016 campaign, when he confronted then-candidate Trump for mocking Sen. John McCainJohn Sidney McCainJeffries blasts Trump for attack on Thunberg at impeachment hearing Live coverage: House panel debates articles of impeachment Budowsky: Would John McCain back impeachment? MORE (R-Ariz.) for being captured during the Vietnam War.

He's publicly urged his party to challenge the president's rhetoric, arguing its doing long-term damage both to the Republican Party and the country's democratic institutions, adding on Thursday that they need constant defense to be upheld.

Flake recounted that, while working in Namibia, he read Czechoslovak President Václav Havel's 1990 speech to Congress in which he urged lawmakers to continue to help the Soviet Union, shortly before it dissolved.

"Vladimir Putin would go on to be president and he is president still, and just as he hijacked democracy in his own country, he is determined to do so everywhere. Denial of this reality will not make it any less real. This is something that is staring us in the face, right now, as we are gathered here today," Flake said.

He added that "we are being powerfully reminded just how delicate all of this is, right now."

Flake characterized himself as "filled with gratitude" and "grateful" for serving in the Senate and said he is "optimistic about the future," but also warned that the country is being tested.

He added that Congress has a "solemn obligation" to the international community as an "authoritarian impulse reasserts itself globally."

"Let us recognize from this place here today that the shadow of tyranny is once again enveloping parts of the globe," he said. "And let us recognize as authoritarianism reasserts itself in country after country that we are by no means immune."

More than 15 of Flake's colleagues, including approximately 10 Republican senators, sat in the chamber and listened to Flake's speech.

Majority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSenate gears up for battle over witnesses in impeachment trial McConnell: I doubt any GOP senator will vote to impeach Trump McConnell says he'll be in 'total coordination' with White House on impeachment trial strategy MORE (R-Ky.) toasted Flake from the Senate floor earlier Thursday, noting his work on earmarks and quipping about him making The Hill's "50 Most Beautiful" list, where he claimed first place in 2013.

"A few years back — now listen to this — he was even named by The Hill newspaper as the No. 1 most beautiful person on Capitol Hill," McConnell said. "Talk about an achievement that few of us could even aspire to."