U.S. President Donald Trump’s lawyers submitted a trial brief Monday calling his impeachment by the House “a dangerous perversion” of the U.S. constitution and demanding his immediate acquittal by the Senate.

Almost simultaneously, House impeachment managers responded to an earlier Trump filing, saying the president had engaged in “corrupt conduct... to cheat in the next election” and that the Senate should remove him from office “following a fair trial.”

The dueling briefs provided the most extensive look yet at the arguments taken by the opposing sides, as they seek to win over not just senators but the U.S. public.

The historic impeachment trial was set to open in earnest at 1 p.m. yesterday local time, first with debate on what rules will govern the trial, overseen by the chief justice of the U.S. Supreme Court, John Roberts.

The two briefs came on what normally would be a quiet federal holiday, Martin Luther King Jr. Day.

But the weeks to come will be anything but normal, as the Senate opens only the third presidential impeachment trial in U.S. history.

In the president’s brief, his 12-man legal team contested the very idea of his impeachment.

They called the two articles of impeachment — approved largely along party lines in the Democrat-controlled House — the product of “a rigged process” and “constitutionally deficient on their face” because they involved no violation of established law.

The brief said the theories underpinning them “would do lasting damage to the separation of powers under the Constitution.”

The brief from the House managers, all Democrats, accused Trump of using “presidential powers to pressure a vulnerable foreign partner to interfere in our elections for his own benefit.”

It added, “In doing so, he jeopardized our national security and our democratic self-governance.”

“He then used his presidential powers to orchestrate a cover-up unprecedented in the history of our republic.”

The two articles of impeachment charge Trump with abuse of power by pressuring Ukraine to provide dirt on Democratic presidential candidate Joe Biden and his son, and of obstructing Congress by refusing to allow top aides to testify.

Key issues surrounding the trial — foremost, whether witnesses can be called and new evidence submitted along with the extensive record compiled during weeks-long House hearings — remain to be determined.

(SD-Agencies)