Everyone was looking to see on Thursday if four moderate Republicans in the US Senate would vote to call witnesses to President Donald Trump’s impeachment trial.
If the four choose to vote with the minority Democrats, it is likely the Senate will invite the former National Security Adviser, John Bolton, who was fired by Mr. Trump at the end of last year.
Senior Republicans, led by Senate Majority Leader Mitch McConnell, had pushed for a speedy trial with no witnesses or new evidence presented at the trial.
But reports that a yet-unpublished book by Mr. Bolton contains damning testimony against President Trump has clearly shifted the calculus.
On Thursday, Senators sat in session for a second day of questions to Democratic impeachment managers and Trump defence lawyers. The senators are expected to vote on witnesses on Friday.
The four Republicans who could be key in the day’s ballot, Senators Mitt Romney, Lisa Murkowski, Susan Collins and Lamar Alexander, have all said they remain undecided on how to vote.
All four would be required to vote with a unanimous Democratic block in order to achieve the necessary Senate majority.
Senator Alexander appeared poised on Thursday to announce his decision, telling the Washington Post that he would make his mind up after the final questions in the Senate chamber.
If Democrats lose the vote, and no witnesses are called, the president could be acquitted of the impeachment charges as soon as Friday. Sixty out of the 100 senators will be required to vote “yes” in order to remove him from office.
Republicans hold a fifty-three-to-forty-seven majority in the Senate.
If all four Republicans decide to vote with Democrats, the trial will go on into next week, although there is little, if any chance that Mr. Trump will be removed by the upper house.