US impeachment managers denounced Donald Trump's alleged incitement of insurrection as "a betrayal of historic proportions" Tuesday as they unveiled their arguments against the former president one week before the Senate begins hearing his case.

"In a grievous betrayal of his oath of office, President Trump incited a violent mob to attack the United States Capitol during the Joint Session, thus impeding Congress's confirmation of Joseph R. Biden, Jr. as the winner of the presidential election," the Democratic lawmakers, led by congressman Jamie Raskin, said in their pre-trial brief to the Senate.

"Failure to convict would embolden future leaders to attempt to retain power by any and all means -- and would suggest that there is no line a President cannot cross," they said, adding that the American people should be protected "against a President who provokes violence to subvert our democracy."

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