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One week ahead of former President Donald Trump's second impeachment trial, House Democrats have outlined the argument for conviction.

Nine impeachment managers on Tuesday filed a brief with the Senate, arguing the former president is "singularly responsible" for last month's deadly attack on the Capitol building and describing his actions as a "betrayal of historic proportions," The Washington Post reports.

"If provoking an insurrectionary riot against a Joint Session of Congress after losing an election is not an impeachable offense, it is hard to imagine what would be," Democrats wrote.

Trump has been charged with "incitement of insurrection" after a mob of his supporters stormed the Capitol building while Congress met to certify the election results, leaving five people dead. With the support of 10 Republicans, the House of Representatives passed an impeachment article last month charging Trump with inciting the riot, making him the first president in American history to be impeached twice.

Democrats wrote in the brief that Trump "summoned a mob to Washington, exhorted them into a frenzy, and aimed them like a loaded cannon down Pennsylvania Avenue," and they argued he must be barred from holding office again.

"It is the electoral process itself that President Trump attacked and that must be protected from him and anyone else who would seek to mimic his behavior," the brief says.

Democrats additionally pushed back against the argument that the second impeachment trial is unconstitutional because Trump is no longer in office, saying a president "must answer comprehensively for his conduct in office from his first day in office through his last." Trump's team is expected to file a response later on Tuesday, writes the Post. The historic impeachment trial is set to begin on Feb. 9.