Watergate reporter Carl Bernstein Carl BernsteinTrump calls Carl Bernstein 'total nut job' after CNN analyst's 'homicidal president' charge Carl Bernstein: Woodward's Trump tapes 'smoking gun' of 'homicidal negligence' Bob Woodward to appear on '60 Minutes' Sunday to discuss new Trump book, 'Rage' MORE accused Republican senators of a "cover-up" while calling President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE's impeachment and likely acquittal "a really shameful episode in our history" during an appearance on CNN Thursday night.

The perspective from the CNN contributor comes as Trump's impeachment trial looks set to be wrapped up as soon as Friday night or Saturday morning. Republican senators appear to have the votes to block Democrats from calling any new witnesses, including former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE.

“They have covered up what the president of the United States has done in his grievous action when they had the the ability to find out more," Bernstein said in lacerating the GOP majority.

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“This is a cover-up, plain and simple," he continued. "And there has been no attempt throughout this proceeding by the Republicans in this Senate of the United States — the so-called world’s greatest deliberative body, which we now can see how deliberative it is — that we have seen now a really shameful episode in our history that’s going to redound for many, many years.”

Sen. Lamar Alexander Andrew (Lamar) Lamar AlexanderMcConnell locks down key GOP votes in Supreme Court fight Alexander backs vote on Trump Supreme Court nominee: What Democrats 'would do if the shoe were on the other foot' Toobin: McConnell engaging in 'greatest act of hypocrisy in American political history' with Ginsburg replacement vote MORE (R-Tenn.), seen as a possible swing vote on witnesses, announced late Thursday after senators concluded a period of asking questions to both legal teams in the impeachment drama, that he would not back a call for new witnesses.

"I worked with other senators to make sure that we have the right to ask for more documents and witnesses, but there is no need for more evidence to prove something that has already been proven and that does not meet the U.S. Constitution's high bar for an impeachable offense," Alexander wrote on Twitter in the first of a series of tweets explaining his decision.