WASHINGTON — Following the dramatic announcement of Sen. Lamar Alexander's decision to vote "no" on subpoenaing any witnesses in the impeachment trial of President Donald Trump, it appears likely that the Senate will likely acquit Trump in the coming days.

Alexander, a moderate Republican from Tennessee, said in a statement late Thursday evening that he would vote "no" on calling witnesses in the trial. He, along with Sens. Susan Collins, Lisa Murkowski and Mitt Romney, have widely been considered the most likely Republican senators to break ranks and call for witnesses.

With the Republican caucus currently holding a 53-47 edge, Democrats would need four GOP senators to vote with them to call witnesses. In the event of a 50-50 tie, Supreme Court Chief Justice John Roberts could break the tie and force witness testimony, but that is unlikely to happen.

Democrats have been calling for former National Security Advisor John Bolton to appear before the Senate as a witness. Earlier this week, reports emerged that Bolton has written a book manuscript in which he writes that Trump told him directly he was withholding military aid earmarked for Ukraine until the country released politically damagiing information about Democratic presidential candidates.

Trump is charged with two articles of impeachment — one count of abuse of power, the other for obstruction of Congress. The House claimed Trump abused the power of the presidency by withholding the military aid in exchange for an announcement that Ukraine would announce an investigation into Joe Biden and his son, Hunter, about Hunter Biden's time on the board of Ukranian energy company, Burisma. They also allege Trump obstructed Congress by not participating in the House's investigation.

After senators vote on witness testimony Friday, they could move to acquit Trump of the impeachment charges. While speaking with Fox News on Thursday, Sen. Ted Cruz, R-Texas, indicated that the Senate might wait until Saturday to acquit Trump.