• Lawyers for Donald Trump in a legal memo denied that he incited the deadly riot at the U.S. Capitol and accused Democrats of "political opportunism."
• The brief came a day before Trump's historic second impeachment trial was set to begin in the Senate.
• Trump's lawyers argued that the trial itself is unconstitutional and must be quickly dismissed.

Lawyers for Donald Trump on Monday denied that he incited the deadly riot at the U.S. Capitol and accused Democrats of "political opportunism" in a fiery brief submitted a day before the former president's historic second impeachment trial was set to begin.

Trump's three lawyers argued in the 78-page brief that the trial itself, which comes nearly three weeks after President Joe Biden was sworn into office, is unconstitutional and must be quickly dismissed.

"Indulging House Democrats hunger for this political theater is a danger to our Republic democracy and the rights that we hold dear," the lawyers wrote.

The legal memo aggressively pushes back on the case laid out last week by Democratic House impeachment managers, which aimed to establish that Trump is "personally responsible" for provoking the Jan. 6 assault on the Capitol by a mob of his supporters.

If convicted, Democrats vow to ban Trump from ever holding federal office again.

But Democrats are unlikely to convince two-thirds of the Senate, which is divided 50-50 between Republicans and Democrats, to vote to convict Trump. Before the trial began, all but five Republican senators voted to dismiss it on the grounds that it was unconstitutional to convict a president after he has left office.

Trump's lawyers fleshed out that argument in their brief. "The Senate is being asked to do something patently ridiculous," the lawyers wrote. "Try a private citizen in a process that is designed to remove him from an office that he no longer holds."

Impeachment managers called that view "dangerous," saying it is "unthinkable" that the framers of the Constitution "left us virtually defenseless against a president's treachery in his final days."

"There is no 'January Exception' to impeachment or any other provision of the Constitution," the Democrats said. "A president must answer comprehensively for his conduct in office from his first day in office through his last."

Some Republican senators have reportedly said that they voted for the motion to dismiss the trial because they wanted to debate the question of constitutionality.

The House impeached Trump on Jan. 13, one week before he left office, on an article of inciting the Capitol riot, which left five dead and forced a joint session of Congress into hiding. At a rally outside the White House shortly before the riot began, Trump urged his followers to march to the Capitol and pressure GOP lawmakers, as well as then-Vice President Mike Pence, to try to overturn Biden's electoral victory.

"If you don't fight like hell you're not going to have a country anymore," Trump told the crowd, among other remarks that Democrats have seized on.

His lawyers argued in the brief Monday that his speech at the pre-riot rally "fell well within the norms of political speech that is protected by the First Amendment."

The defense team — comprising Bruce Castor Jr. and David Schoen, as well as Michael van der Veen — also asserted that the trial was a "brazen political act" fueled by Democrats' "fevered hatred for Citizen Trump and their 'Trump Derangement Syndrome.'"