Watch Live: Senate expected to vote on witnesses in Trump's impeachment trial

WASHINGTON (WFLA) – President Donald Trump’s impeachment trial could come to an abrupt end after Friday’s expected vote on witnesses.

The expected debate and vote on bringing new witnesses in for testimony comes after the Senate sat through 16 total hours of questioning on Wednesday and Thursday. Senators questioned prosecutors and the president’s defense team on the cases both sides made in their opening arguments.

Democrats have been ramping up their push for witnesses since an unpublished draft of Jim Bolton’s book surfaced. In that book, the former national security adviser alleges that the president said he wanted to withhold aid from Ukraine until the country helped with investigations into Joe Biden. The president and his defense team have denied those claims.

Since that news, some Republican Senate members – like Sen. Susan Collins of Maine and Sen. Mitt Romney of Utah – have expressed interest in hearing from witnesses like Bolton. Another Republican who was considered a swing vote – the retiring Sen. Lamar Alexander of Tennessee – said Thursday night he would vote against witnesses.

In order for witnesses like Bolton or Mick Mulvaney to testify in the trial, all Senate Democrats would need to vote to call them and four Republicans would need to join them.

The vote is expected to happen at some point on Friday. If the Senate votes against new witnesses, the president’s trial could end quickly with a likely acquittal. If they vote to hear from witnesses, the trial would extend several days, weeks or even months.

Nexstar is bringing you complete coverage of the impeachment trial. Our coverage continues Friday at 1:50 p.m. ET with Evan Donovan, Mahsa Saeidi and Nexstar DC correspondent Kellie Meyer.