Democratic lawmakers prosecuting Donald Trump are set to detail their case against him Wednesday at his impeachment trial, in a longshot bid to convince skeptical Republican senators they should convict the former president.

Trump's second impeachment trial opened Tuesday with Democrats showing harrowing video footage of his supporters' January 6 assault on the US Capitol, where they smashed down doors, broke into the Senate chamber and led riots that left five people dead.

Trump faces a single charge of inciting the insurrection after he told enraged Republican supporters near the White House to "fight like hell."

Securing a conviction is highly unlikely, as the Democrats would need 17 Republican senators to vote with them to make a two-thirds majority. 

So far, only six Republicans have agreed that the trial is even constitutional in the first place.

Following Tuesday's opening statements from Democratic "impeachment managers" and Trump's lawyers, both sides will flesh out their cases starting Wednesday, with the Democrats going first.

Under impeachment rules, each side is allowed up to 16 hours over two days to present their case, starting at noon (1700 GMT).

Senators will also be given a total of four hours for questioning.

Narrowly bipartisan vote

On Tuesday, senators voted 56-44 in favor of the constitutionality of the historic trial, rejecting a bid by Trump's lawyers to throw it out on grounds that a former president cannot be tried by lawmakers.

Earlier, both sides presented their opening cases, with Democrats arguing that Trump broke his oath in a naked bid to retain power after losing the November election to Joe Biden.

Refusing to accept his defeat, Trump spread lies about vote rigging and repeatedly pressured officials, including then vice president Mike Pence, to try and stop the transfer of power.

"If Congress were to just stand completely aside in the face of such an extraordinary crime against the Republic, it would invite future presidents to use their power without any fear of accountability," Democratic impeachment manager Joe Neguse said.

Video from the mayhem played back inside the ornate Senate packed Tuesday's biggest punch.

Senators -- who witnessed the events firsthand when they had to be rushed to safety -- watched raw footage of Trump's speech and the crowd's ensuing assault on the Capitol.

The video montage showed the mob chanting pro-Trump slogans as it smashed through doors, swarmed police, and managed for the first time in history to disrupt the Congressional vote certifying the election.

"If that's not an impeachable offense, then there is no such thing," lead impeachment manager Jamie Raskin said.

Trump lawyer David Schoen, however, said the Senate had no jurisdiction to try Trump once he had left office and warned that the impeachment threatened to "tear this country apart."

It will leave the United States "far more divided and our standing around the world will be badly broken," he argued.

Record-setting

Republican Senator Bill Cassidy, who voted to allow the trial to proceed, tweeted that the Democrats had "much stronger constitutional arguments" than Trump's lawyers.

Independent Senator Bernie Sanders, who votes with Democrats, told AFP he thought the first day of the trial was "interesting," but he would not be drawn on whether he believed the compelling video montage would sway Republicans.

Trump is the first president ever to face two impeachment trials -- he was already acquitted in 2020 of abuse of power -- as well as the first in history to be tried after leaving the White House.

His team is basing its case largely on the procedural argument that a former president cannot be tried, calling the Senate trial "absurd."

They also argue that whatever Trump said during his January 6 rally is protected by the constitutional right to free speech and did not amount to ordering the assault on Congress.

A second acquittal is all but certain for Trump, who is holed up in his luxury Mar-a-Lago resort in Florida.

Amped up on four years of Trump's populist claims to be fighting for ordinary people against the elites, huge numbers of Republican voters continue to support the ex-president, pushing their party further to the right.