Donald Trump’s historic second impeachment trial is opening Tuesday with a sense of urgency, by Democrats who want to hold the former president accountable for the violent U.S. Capitol siege and Republicans who want it over as fast as possible.

Trump is the third American president to be impeached and the first to be impeached twice.

In late 2019, the Democrat-led U.S. House impeached him on two charges: abuse of power and obstruction of Congress. The GOP-led Senate acquitted Trump on both charges in February 2020. Prior to Trump, only Andrew Johnson and Bill Clinton had been impeached. Both were also acquitted by the Senate.

The latest impeachment charge — authored by U.S. Reps. David Cicilline of Rhode Island, Jamie Raskin of Maryland and Ted Lieu of California — alleges Trump incited the violence that led to a deadly riot at the U.S. Capitol on Jan. 6.

One Capitol Police officer, Brian David Sicknick, died from injuries suffered in the riot. One protester — Trump supporter Ashli Babbitt, 35, who was a 14-year U.S. Air Force veteran — was shot to death during the protest.

The riot began when Trump supporters descended on the nation’s capital the same day as Congress began certifying the Electoral College vote, which assured Democrat Joe Biden the presidency. More Americans in history cast their ballot before and during the Nov. 3 presidential election, and Biden secured an overwhelming majority of the popular vote — more than 80 million — and electoral votes, 306. A total of 270 Electoral College votes are needed to win the White House.

However, before and after the election, Trump continued to make widespread allegations about the integrity of the electoral process and claimed massive voter fraud. His legal teams filed numerous lawsuits in several battleground states, all of which have been dismissed by those respective judges.

Before the riot, Trump addressed his supporters, thousands of whom then marched to the U.S. Capitol and breached the building. Congress and staff were forced to evacuate the building and forced into recess until the violence could be contained. Later that evening and stretching into the next day, Congress officially certified the Electoral College totals, ensuring Biden’s win as the nation’s 46th president.

After weeks of delays and legal challenges, Trump eventually acknowledged Biden’s victory, though he never conceded the election.

Approving one impeachment charge of “incitement of insurrection,” the Democrat-led House impeached Trump on Jan. 13, one week before his term was to have ended anyway. The unprecedented second impeachment of an American president came without hearings, witnesses or testimony.

Scheduled to begin Tuesday, just over a month since the deadly riot, the proceedings are expected to diverge from the lengthy, complicated trial that resulted in Trump’s acquittal a year ago on charges that he privately pressured Ukraine to dig up dirt on Biden. This time, Trump’s Jan. 6 rally cry to “fight like hell” and the storming of the Capitol played out for the world to see.

While Trump is almost certain to be acquitted again, the trial could be over in half the time.

Details of the proceedings are still being negotiated by the Senate leaders, with the duration of opening arguments, senators’ questions and deliberations all up for debate.

So far, it appears there will be few witnesses called, as the prosecutors and defense attorneys speak directly to senators who have been sworn to deliver “impartial justice” as jurors. Most are also witnesses to the siege, having fled for safety that day as the rioters broke into the Capitol and temporarily halted the electoral count certifying Biden’s victory.

Defense attorneys for Trump declined a request for him to testify.

Instead, House managers prosecuting the case are expected to rely on the trove of videos from the siege, along with Trump’s incendiary rhetoric refusing to concede the election, to make their case. His new defense team has said it plans to counter with its own cache of videos of Democratic politicians making fiery speeches.

“We have the unusual circumstance where on the very first day of the trial, when those managers walk on the floor of the Senate, there will already be over 100 witnesses present,” said Rep. Adam Schiff, D-California, who led Trump’s first impeachment. “Whether you need additional witnesses will be a strategic call.”

Democrats argue it’s not only about winning conviction but also holding the former president accountable for his actions, even though he’s out of office. For Republicans, the trial will test their political loyalty to Trump and his enduring grip on the GOP.

Initially repulsed by the graphic images of the siege, Republican senators including Senate Republican leader Mitch McConnell denounced the violence and pointed a finger of blame at Trump. But in recent weeks GOP senators have rallied around Trump arguing his comments do not make him responsible for the violence. They question the legitimacy of even conducting a trial of someone no longer in office.

On Sunday, Republican Sen. Roger Wicker of Mississippi described Trump’s impeachment trial as a “meaningless messaging partisan exercise.” Republican Sen. Rand Paul of Kentucky called the proceedings a farce with “zero chance of conviction” and described Trump’s language and rally words as “figurative” speech.

Senators were sworn in as jurors late last month, shortly after Biden was inaugurated, but the trial proceedings were delayed as Democrats focused on confirming the new president’s initial Cabinet picks and Republicans sought to put as much distance as possible from the riot.

At the time, Paul forced a vote to set aside the trial as unconstitutional because Trump is no longer in office, drawing 44 other Republicans to his argument.

A prominent conservative lawyer, Charles Cooper, rejects that view, writing in a Wall Street Journal opinion piece Sunday that the Constitution permits the Senate to try an ex-official, a significant counterpoint to that of Republican senators who have looked toward acquittal by advancing constitutional claims.

Republican Sen. Lindsey Graham of South Carolina, one of Trump’s ardent defenders, said he believes Trump’s actions were wrong and “he’s going to have a place in history for all of this,” but insisted it’s not the Senate’s job to judge.

“It’s not a question of how the trial ends, it’s a question of when it ends,” Graham said. “Republicans are going to view this as an unconstitutional exercise, and the only question is, will they call witnesses, how long does the trial take? But the outcome is really not in doubt.”

Forty-five votes in favor of Paul’s measure suggested the near impossibility of reaching a conviction in a Senate in which Democrats hold 50 seats but a two-thirds vote — or 67 senators — would be needed to convict Trump. Only five Republican senators joined with Democrats to reject Paul’s motion: Mitt Romney of Utah, Ben Sasse of Nebraska, Susan Collins of Maine, Lisa Murkowski of Alaska and Pat Toomey of Pennsylvania.