President Trump on Tuesday angrily denounced the looming House votes to impeach him as a “Star Chamber of partisan persecution” by Democrats, describing the effort to remove him from office as an “attempted coup” that would come back to haunt them at the ballot box next year.

On the eve of the historic votes, Democrats reached a critical threshold, gathering majority support to impeach Trump, as the President raged against the proceedings. In an irate and rambling six-page letter to Speaker Nancy Pelosi, Trump portrayed himself as the victim of enemies determined to destroy his presidency with false accusations.

“This is nothing more than an illegal, partisan attempted coup that will, based on recent sentiment, badly fail at the voting booth,” Trump declared, describing a process enshrined in the Constitution as an attempted government overthrow.

“History will judge you harshly as you proceed with this impeachment charade,” he wrote.

In a missive full of unproven charges, hyperbole and long-simmering grievances against his own government — at one point, he referred to leaders of the FBI as “totally incompetent and corrupt” — Trump angrily disputed both of the impeachment charges: abuse of power and obstruction of Congress.

The letter ignored the extensive evidence uncovered during a two-month inquiry by the House Intelligence Committee, based in part on the testimony by members of his own administration.

It found that Trump sought to pressure Ukraine to investigate his political rivals while holding back nearly $400 million in military assistance the country badly needed and a White House meeting for its President.

The charges accuse Trump of engaging in a corrupt scheme to enlist a foreign power for his own political benefit in the 2020 election, followed by an effort to conceal his actions by blocking congressional investigations. On Wednesday, the House is all but certain to approve them on nearly party-line votes, making him the third President ever to be impeached.

Past Presidents have offered contrition as they stared down looming House impeachment votes. President Bill Clinton issued a personal apology from the White House Rose Garden in 1998, biting his lip and saying he was “profoundly sorry” for his actions in the Monica Lewinsky affair days before the House voted to impeach him. President Richard M. Nixon resigned his office in 1974 rather than face the vote at all.

But Trump was defiant and unrepentant on Tuesday. He accused Pelosi and her party of fabricating lies, saying that the Speaker and Democrats were possessed by “Impeachment Fever” and vowing that he and the Republican Party would emerge stronger after he was vindicated in a Senate trial.

“You are the ones interfering in America’s elections,” he wrote in the letter, on stationery embossed with the presidential seal. You are the ones subverting America’s democracy. You are the ones Obstructing Justice. You are the ones bringing pain and suffering to our Republic for your own selfish personal, political, and partisan gain.”

The letter appeared to preview the grievance-filled narrative of Trump’s 2020 campaign, echoing the rants he delivers at arena-style rallies around the country as he campaigns for re-election.

The President wrote that he knew his letter would not change the outcome.

But he said that the document was “for the purpose of history and to put my thoughts on a permanent and indelible record”.

In her own message on Tuesday evening to Democratic lawmakers, Pelosi made no reference to the President’s letter, instead urging her colleagues to “proceed in a manner worthy of our oath of office to support and defend the Constitution of the United States”.