President Donald Trump's impeachment trial could begin on Inauguration Day, just as Democrat Joe Biden takes the oath of office in an extraordinary end to the defeated president's tenure in the White House.
The trial timeline and schedule are largely set by Senate procedures and will start as soon as the House delivers the article of impeachment. That could mean starting the trial at 1pm on Inauguration Day. The ceremony at the Capitol starts at noon.
Trump was impeached Wednesday (US time) by the House over the deadly Capitol siege, the only president in US history twice impeached, after a pro-Trump mob stormed the building. The attack has left the nation's capital, and other capital cites, under high security amid threats of more violence around the inauguration.
House Speaker Nancy Pelosi has not said when she will take the next step to transmit the impeachment article, a sole charge of incitement of insurrection. Some senior Democrats have proposed holding back the article to give Biden and Congress time to focus on his new administration's priorities.
Biden has said the Senate should be able to split its time and do both.
The impeachment trial will be the first for a president no longer in office. And, politically, it will force a reckoning among some Republicans who have stood by Trump throughout his presidency and largely allowed him to spread false attacks against the integrity of the 2020 election.
Senate Republican leader Mitch McConnell is open to considering impeachment, having told associates he is done with Trump, but has not signalled how he would vote.
Convening the trial will be among his last acts as majority leader, as two new senators from Georgia, both Democrats, are to be sworn into office leaving chamber divided 50-50. That tips the majority to the Democrats once Kamala Harris takes office, as the vice president is a tie-breaker.
In a note to colleagues Wednesday, McConnell said he had "not made a final decision on how I will vote" in a Senate impeachment trial.
With the Capitol secured by armed National Guard troops inside and out, the House voted 232-197 to impeach Trump. The proceedings moved at lightning speed, with lawmakers voting just one week after violent pro-Trump loyalists stormed the Capitol, egged on by the President's calls for them to "fight like hell" against the election results.
Ten Republicans fled Trump, joining Democrats who said he needed to be held accountable and warned ominously of a "clear and present danger" if Congress should leave him unchecked before Democrat Joe Biden's inauguration January 20. It was the most bipartisan presidential impeachment in modern times, more so than against Bill Clinton in 1998.
The Capitol insurrection stunned and angered lawmakers, who were sent scrambling for safety as the mob descended, and it revealed the fragility of the nation's history of peaceful transfers of power.
Pelosi invoked Abraham Lincoln and the Bible, imploring lawmakers to uphold their oath to defend the Constitution from all enemies, foreign "and domestic".
She said, of Trump: "He must go, he is a clear and present danger to the nation that we all love."
Holed up at the White House, watching the proceedings on TV, Trump later released a video statement in which he made no mention at all of the impeachment but appealed to his supporters to refrain from any further violence or disruption of Biden's inauguration.
"Like all of you, I was shocked and deeply saddened by the calamity at the Capitol last week," he said, his first condemnation of the attack. He appealed for unity "to move forward" and said, "Mob violence goes against everything I believe in and everything our movement stands for. ... No true supporter of mine could ever disrespect law enforcement."
Trump was first impeached by the House in 2019 over his dealings with Ukraine, but the Senate voted in 2020 acquit.
No president has been convicted by the Senate, but Republicans have said that could change in the rapidly shifting political environment as officeholders, donors, big business and others peel away from the defeated president.
Conviction and removal of Trump would require a two-thirds vote in the Senate.
Biden said in a statement after the vote that it was his hope the Senate leadership "will find a way to deal with their Constitutional responsibilities on impeachment while also working on the other urgent business of this nation".
Unlike his first time, Trump faces this impeachment as a weakened leader, having lost his own reelection as well as the Senate Republican majority.
In making a case for the "high crimes and misdemeanours" demanded in the Constitution, the four-page impeachment resolution relies on Trump's own incendiary rhetoric and the falsehoods he spread about Biden's election victory, including at a rally near the White House on the day of the January 6 attack on the Capitol.
The impeachment resolution is also intended to prevent Trump from ever running again.
A Capitol Police officer died from injuries suffered in the riot, and police shot and killed a woman during the siege. Three other people died in what authorities said were medical emergencies. The riot delayed the tally of Electoral College votes which was the last step in finalising Biden's victory.
Ten Republican lawmakers, including third-ranking House GOP leader Liz Cheney of Wyoming, voted to impeach Trump, cleaving the Republican leadership, and the party itself.
Cheney, whose father is the former Republican vice president, said of Trump's actions summoning the mob that "there has never been a greater betrayal by a President" of his office.
The president's sturdy popularity with the GOP lawmakers' constituents still had some sway, and most House Republicans voted not to impeach.
Trump was said to be livid with perceived disloyalty from McConnell and Cheney.
Security was exceptionally tight at the Capitol, with tall fences around the complex. Metal-detector screenings were required for lawmakers entering the House chamber, where a week earlier lawmakers huddled inside as police, guns drawn, barricaded the door from rioters.
The impeachment bill draws from Trump's own false statements about his election defeat to Biden. Judges across the country, including some nominated by Trump, have repeatedly dismissed cases challenging the election results, and former Attorney General William Barr, a Trump ally, has said there was no sign of widespread fraud.
While some have questioned impeaching the president so close to the end of his term, there is precedent. In 1876, during the Ulysses Grant administration, War Secretary William Belknap was impeached by the House the day he resigned, and the Senate convened a trial months later. He was acquitted.