Republicans raise questions about the trial’s constitutionality, signalling an uphill battle for Trump’s conviction.

The United States Senate is moving forward with a trial of former President Donald Trump on an impeachment charge of incitement of insurrection for his role in the January 6 attack on the US Capitol by his supporters.

The Senate voted 55 to 45 to reject an objection against the proceedings raised by a Republican senator on grounds that the US constitution does not provide for impeachment of former presidents.

The vote clears the way for a Senate trial to begin but signals most Republicans oppose the proceedings and suggests Trump may avoid conviction.

Republican Senator Rand Paul argued that because Trump is now a “private citizen”, the US constitution does not authorise the Senate to conduct an impeachment trial.

“The theory that the impeachment of a former official is unconstitutional is flat-out wrong,” Senate Majority Leader Chuck Schumer said on the Senate floor prior to the vote.

“It’s been completely debunked by constitutional scholars from all across the political spectrum,” added Schumer.

The Senate adopted rules for the presentation of evidence and arguments in the trial and issued a summons to Trump commanding him to respond to the impeachment charge.

House managers and Trump’s legal defence team now have until February 8 to file a series of legal briefs and documents. The Senate will reconvene on February 9 for the trial.

Before the mob attack on the Capitol, US President Donald Trump told a rally of his supporters to ‘fight like hell’ to contest the certification of the 2020 US presidential election results by the Congress on January 6 [Jim Bourg/Reuters]

“Calmer heads have typically prevailed in our history and allowed public opinion to cast blame where blame is deserved,” Paul said in Senate floor remarks.

“This sham of an impeachment will ostensibly ask whether the president incited the reprehensible behaviour and violence of January 6 when he said, ‘I know everyone here will soon march to the Capitol to peacefully and patriotically make your voices heard’,” Paul said, reciting a line from Trump’s speech.

“Peacefully and patriotically, those are hardly words of violence,” Paul said.

Senator Rand Paul is trailed by reporters as he arrives to be sworn in for the impeachment trial of former President Donald Trump in the US Capitol in Washington [Jonathan Ernst/Reuters]

The House impeached Trump on January 13 on a single charge of “incitement of insurrection” making him the first president in US history to be impeached twice.

Trump had refused the concede the outcome of the 2020 election of Joe Biden as the next US president and he assembled his supporters in Washington for a rally on January 6, the same day Congress was meeting in joint session to ratify Biden’s election win.

In a speech outside the White House, Trump exhorted the crowd to march on the Capitol where Congress was meeting.

The former president urged his supporters to “fight like hell” to stop Biden from being confirmed as president. Thousands marched to the Capitol and a mob of hundreds stormed the building, sending lawmakers into hiding and resulting in five deaths.

Senator Patrick Leahy, the senior Democrat designated as the president pro tempore of the Senate, will preside over the trial and serve as a juror.

All of the remaining 99 senators were sworn in as jurors with each walking to the well of the Senate chamber to sign their oath of impartiality.

The US House of Representatives had presented its article of impeachment against Trump to the Senate on Monday evening, a step that formally set in motion the Senate trial.

Walking from one side of the US Capitol to the other, nine House managers appointed by Speaker Nancy Pelosi hand-delivered the impeachment document to the Senate.

The article charges Trump over the deadly storming on January 6 of the US Capitol building in Washington, DC, by a mob of his supporters.

Representative Jamie Raskin, a constitutional scholar and one of the House managers, will be acting as a prosecutor in the Senate trial.

“President Trump repeatedly issued false statements asserting that the presidential election results were the product of widespread fraud, and should not be accepted by the American people, or certified by state or federal officials,” Raskin told the Senate on Monday.

To be convicted, the Senate must secure a two-thirds majority on the impeachment charge.

If that happens, a subsequent vote could bar Trump from running for public office again in the future.