Her remarks came the day after the House — with support from 10 Republicans — impeached the president on a single charge of “incitement of insurrection,” and as Republicans faced the prospect of a trial that could begin as soon as next week.
Republicans were racing to gauge the political dynamics of a vote to convict Mr. Trump, which would open the door to disqualifying him from holding office in the future. Most of them kept their powder dry publicly, but were privately struggling to reconcile their own disdain for the leader they supported loyally for years and their fear of a backlash from a political base more devoted to Mr. Trump than any other party figure.
Though few Republicans had gone on record in such stinging terms, Ms. Murkowski was not alone in breaking from the president. Senators Mitt Romney of Utah, Ben Sasse of Nebraska, Patrick J. Toomey of Pennsylvania and Susan Collins of Maine had spoken out harshly against Mr. Trump, leaving colleagues to speculate that they could vote to convict him and bar him from ever holding office again.
Even Senator Mitch McConnell of Kentucky, the Republican leader, indicated to colleagues that he was undecided about whether to convict Mr. Trump, and privately told advisers he approved of the impeachment drive and believed it could help the party purge Mr. Trump.
Others in the party, led by Senator Lindsey Graham of South Carolina, were pushing back hard against a conviction, warning it would harm the party and the country, as federal authorities cautioned about continued violent threats from pro-Trump extremists.