Collins announced on Tuesday that she would vote to acquit Trump on the two House-passed impeachment articles: abuse of power and obstruction of Congress.

She said during a floor speech that the House didn't meet the "burden of showing that the president's conduct, however flawed, warrants the extreme step of immediate removal from office."

Collins is one of 15 current senators who also served in the Senate during the 1999 Clinton trial. She voted during that proceeding to find Clinton not guilty of both articles of impeachment.

Clinton apologized during a national address after the Senate acquitted him and said that he was "humbled and very grateful" for the support and prayers he received during the trial.

"I want to say again to the American people how profoundly sorry I am for what I said and did to trigger these events and the great burden they have imposed on the Congress and on the American people," he said.

GOP senators have labeled Trump's request that Zelensky "look into" the Bidens and his decision to delay the Ukraine aid as "shameful," "inappropriate" and "improper." But no GOP senator has said yet that they would vote to convict him or that they would support a formal reprimand of Trump.

But Collins appeared to close the door to that idea on Tuesday, telling CBS that the House's decision to impeach Trump is a bigger punishment than censure.

"I think we're past that point. We've had the president impeached," she said. "That is a far greater sanction than a censure. I think we're past that stage."