House Democrats said the evidence was “overwhelming” that Donald Trump committed a “grievous betrayal of his oath of office”, while the former US president’s lawyers insisted he was merely exercising his right to free speech, ahead of his second impeachment trial.

Mr Trump was impeached last month in a bipartisan vote in the House of Representatives on a charge of inciting an insurrection in connection with the January 6 siege on the US Capitol, when a mob of his supporters stormed the legislative complex in an attack that left five people dead. Shortly before the siege, Mr Trump told the crowds: “If you don’t fight like hell, you’re not going to have a country any more.”

In a brief filed on Tuesday, House Democrats — who will act as impeachment managers, or prosecutors, in the Senate trial — said Mr Trump had “singular responsibility” for the “tragedy”.

“It is impossible to imagine the events of January 6 occurring without President Trump creating a powder keg, striking a match, and then seeking personal advantage from the ensuing havoc,” they wrote.

Mr Trump has largely stayed out of the public eye since snubbing Joe Biden’s inauguration and is now living at his Mar-a-Lago resort in Florida. His lawyers, David Schoen and Bruce Castor Jr, who were hired after the former president’s initial legal team quit last week, set out their own case in a separate brief on Tuesday.

Mr Trump’s lawyers argued that he “at all times . . . fully and faithfully executed his duties as president of the United States” and said the former president had “exercised” his free-speech rights under the First Amendment of the Constitution to “express his belief that the election results were suspect” in the run-up to the Capitol assault.

Mr Trump is just the third president in US history to be impeached, and the only one to be impeached twice. He was first impeached in December 2019 on two charges relating to his efforts to get the Ukrainian president to dig up dirt on Mr Biden and his son, Hunter. Mr Trump was acquitted on both charges after just one Republican senator, Mitt Romney, broke ranks with his party and voted to convict.

Mr Trump’s second Senate trial will begin in earnest next week. It remains unlikely that he will be convicted, however, given the upper chamber of Congress is split, 50-50, and all but five Senate Republicans last week backed a motion calling into question whether it was constitutional to try a former president. Two-thirds of the chamber would need to find Mr Trump guilty in order for him to be convicted.

In their brief, Mr Trump’s lawyers argued that he could not be tried because he is now a private citizen and no longer in office.

But House impeachment managers argued that the Senate still had jurisdiction over Mr Trump, even though he left the White House last month. Democrats want to convict the former president and bar him from holding future office.

“The text and structure of the Constitution, as well as its original meaning and prior interpretations by Congress, overwhelmingly demonstrate that a former official remains subject to trial and conviction for abuses committed in office,” the managers wrote in their brief.

They added: “The Constitution governs the first day of the president’s term, the last day, and every moment in between. Presidents do not get a free pass to commit high crimes and misdemeanours near the end of their term.”