Democratic lawmakers rejected Donald Trump’s efforts to throw out the impeachment case against him, one day before the former president’s Senate trial over his role in the siege on Capitol Hill was set to begin.

Trump’s lawyers, Bruce Castor Jr, David Schoen and Michael van der Veen, filed a memo on Monday arguing the article of impeachment was “unconstitutional for a variety of reasons” that were “grounds for immediate dismissal”.

The former president’s lawyers said that “indulging House Democrats’ hunger for this political theatre” would endanger democracy. Joined by several Republican lawmakers, they have argued the trial is not constitutional because Trump is no longer in office, having left the White House when Joe Biden was sworn in on January 20.

House Democrats serving as impeachment managers replied in a separate memo that the “evidence of President Trump’s conduct is overwhelming”.

“He has no valid excuse or defence for his actions,” they wrote. “And his efforts to escape accountability are entirely unavailing.”

Trump was impeached last month in a bipartisan vote in the House of Representatives, when 10 Republican members of Congress joined all of the House Democrats in voting to charge him with inciting an insurrection over his role in the January 6 siege on the Capitol. The vote made Trump the first US president to be impeached for a second time.

Supporters of the former president stormed the legislative complex in a bid to interrupt the certification of Biden’s Electoral College victory, in a violent melee that left five people dead, including a Capitol police officer.

Hours earlier, Trump had told crowds on the national mall: “If you don’t fight like hell, you’re not going to have a country any more.”

The impeachment managers, Democratic lawmakers appointed by House Speaker Nancy Pelosi to act as prosecutors in a Senate trial, delivered the article of impeachment to the Senate last month. A trial in the upper chamber of Congress, with senators acting as jurors, is set to begin on Tuesday.

Last month, 45 of 50 Senate Republicans backed a motion declaring the trial unconstitutional. However, the motion failed to scupper the trial because five Republicans voted with the Democrats, who control the upper chamber.

That vote signalled the likelihood that Trump will be exonerated given the constitution stipulates conviction requires the support of two-thirds of the Senate, which would require 17 Republicans, assuming all 100 senators cast their votes.

More than 150 legal scholars, including the founder and several members of the conservative Federalist Society, said in an open letter last month that the trial was constitutional, given that Trump had committed the offences while in office and the US constitution includes provisions for barring politicians from holding future public positions.

The impeachment managers said in their response on Monday that they would “establish at trial that President Trump merits conviction and disqualification to hold and enjoy any office of honour, trust, or profit under the United States”.

Chuck Schumer, the Democratic Senate majority leader, said he had struck a deal with top Senate Republican Mitch McConnell, the House impeachment managers and Trump’s legal team over how to structure the trial.

Proceedings will begin Tuesday with up to four hours of debate over whether the trial itself is constitutional, followed by a vote where a simple majority is expected to confirm that the Senate has jurisdiction to try Trump.

From Wednesday, each side is expected to use up to two days to set out its case, followed by a period in which senators will be allowed to pose questions. After that — likely early next week — the chamber will consider whether to call witnesses. Trump’s lawyers have already said he will not accept House impeachment managers’ request for him to testify under oath.

The trial will be held every day except Saturdays, after a request from Trump’s legal team to observe the Jewish sabbath, which takes place from sundown on Friday to sundown on Saturday.