Watch live: Trump impeachment trial nears end of initial phase in Senate

Senate Majority Leader Mitch McConnell is shown walking in the hallways of the Capitol building and wearing a dark suit.

The US Senate will hold a second day of questions for the prosecution and defense in the impeachment trial of President Donald Trump before turning on Friday to debate and possibly vote on whether to call witnesses such as former national security adviser John Bolton. Watch the Senate proceedings stream live here starting at 1 p.m. ET.

Republicans who control the Senate said there was a chance the trial could end on Friday with Trump’s acquittal, leaving him in office and rendering moot the articles of impeachment Democrats approved in the House of Representatives in December.

Related: Impeachment trial in the Senate — what’s happening?

An acquittal would allow the Republican president to claim vindication and put the threat to his presidency behind him just as Americans begin focusing on the Democratic race to choose his challenger in the Nov. 3 election.

Iowa holds the first election contest of the year on Monday. Trump will be there on Thursday night for a rally.

Lawyers for Trump and the House Democrats who are managing the impeachment prosecution will spend a second day on Thursday answering questions about the case written down by lawmakers and read aloud by black-robed US Chief Justice John Roberts.

Then, probably on Friday, each side will present what amount to closing arguments, before the senators move to the central question of whether to call witnesses.

Democrats are demanding witnesses in order to shed more light on Trump’s attempt to persuade Ukraine President Volodmyr Zelenskiy to investigate Democratic rival Joe Biden.

To force the issue, they need to persuade at least four Republican senators to vote with them to assure a majority vote in the 100-seat chamber, an effort the top Democrat in the Senate has called an uphill fight.

Even if witnesses are called, Democrats hold out scant hope of ultimately mustering the two-thirds majority needed to remove Trump from office.

Timeline: How Trump was impeached

Bolton this week emerged as a potential witness after a report — which he has not denied — that he planned to say in an upcoming book that Trump told him he wanted to freeze $391 million in US military aid for Ukraine until it investigated Biden and the former vice president’s son, Hunter.

Democratic Representative Jerrold Nadler of New York argued that Trump wanted to “rig an election” by inviting foreign interference in the 2020 election.

“The facts are the facts,” said Nadler. “The president is a danger to the United States … and he must be brought to heel.”

Senator John Barrasso, the No. 3 Republican in seniority, said it was possible the trial could end on Friday without witnesses being called in spite of pressure from Democrats.

“The momentum is clearly in the direction of moving to final judgment on Friday,” he said. Other Republican senators were predicting a similar outcome.

Democrats were not conceding defeat, however.

“There’s tremendous pressure from a vindictive, nasty president on every Republican senator, but I think (as) they sit there … we’ve got a real shot to get witnesses and documents,” Senate Democratic leader Chuck Schumer said on Wednesday.

While the Senate is expected to acquit Trump and leave him in office no matter what happens, allowing witnesses could inflict political damage on him as his re-election bid picks up steam.

By Richard Cowan and David Morgan/Reuters

Sign up for our daily newsletter

Sign up for The Top of the World, delivered to your inbox every weekday morning.