Republican Senator Bill Cassidy of Louisiana, among six GOP senators who broke from the party to vote to proceed with Donald Trump's impeachment trial, said video footage from the Capitol insurrection showed "insurrectionists that tried to object to the peaceful transfer of power".
"That should give anyone who loves our republic great pause," he told reporters on Wednesday.
House impeachment managers on the second day of the former president's impeachment trial included a comprehensive video timeline, aided by previously unreleased surveillance footage and police audio, revealing the scale of the assault on the Capitol on 6 January, and how close lawmakers and their staff came to violence.
Impeachment managers linked the former president's months-long attempt to undermine election results as he courted violence from his supporters, exploding into a deadly insurrection fuelled by his false claims of voter fraud and conspiracy theories.
The footage "reinforces my belief that it was a terrible day for our country, and that there's no doubt that it was an attempt to disrupt the counting of the electoral votes", said Senator Susan Collins, among Republicans who are expected to vote to convict the former president for inciting the insurrection during a joint session of Congress to certify the results of the 2020 presidential election.
She called the hours-long arguments and video presentations from House Democrats serving as trial prosecutors "riveting" and "compelling".
Senator Collins told reporters that the Senate chamber was quiet enough to "hear a pin drop" during the hearing.
"It was obviously very troubling to see the great violence that our Capitol Police and others were subjected to,” said Republican Senator Mitt Romney, who has also suggested voting to convict Mr Trump.
“It tears at your heart and brings tears to your eyes," he told reporters. "That was overwhelmingly distressing and emotional.”
Republican Senator Lisa Murkowski, another Trump critic, said: "I’m angry. I’m disturbed. I’m sad."
"I don't see how Donald Trump could be re-elected to the presidency again," she added. "I just don't see that."
Several other Republican senators told reporters that while the House impeachment managers' presentations were moving and effective, they did not say whether the argument has convinced them to convict.
Senator Rob Portman said he was "impressed" with Democrats' presentation but has not decided whether he will vote to convict, as he believes it's a "bad precedent" to impeach a president who is no longer in office.
"I'm listening, I'm a juror," he said.
Senator Jerry Moran called the violence "graphic" and "disgusting".
"It was a terrible set of circumstances and a heart-wrenching set of videos," he said, adding that he will wait until the conclusion of the trial to make a decision whether to convict.
Minority Whip John Thune told reporters that the prosecution did a "good job connecting the dots, and the President's Twitter feed is a matter of public record."
Impeachment managers did an "effective job of going back several months and showing that public record," he said.
The trial will continue with additional arguments from Democrats on Thursday, followed by up to 16 hours of remarks from the former president's attorneys mounting their defence.
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