Sen. Lamar Alexander (R-Tenn.) announced late Thursday night, Jan. 30, that he would vote against calling additional witnesses in the President Donald Trump’s impeachment trial.

“I worked with other senators to make sure that we have the right to ask for more documents and witnesses, but there is no need for more evidence to prove something that has already been proven and that does not meet the United States Constitution’s high bar for an impeachable offense,” Alexander wrote in a statement released shortly after the Senate impeachment trial question-and-answer phase wrapped up.

“There is no need for more evidence to conclude that the president withheld United States aid, at least in part, to pressure Ukraine to investigate the Bidens; the House managers have proved this with what they call a ‘mountain of overwhelming evidence.” he added. “There is no need to consider further the frivolous second article of impeachment that would remove the president for asserting his constitutional prerogative to protect confidential conversations with his close advisers.”

Alexander’s decision made it significantly less likely that Democrats will have enough votes to hear from former National Security Adviser John Bolton and other witnesses, paving the way for President Trump’s imminent acquittal.

Sen. Susan Collins (R-Maine) announced Thursday evening that she would support calling a “limited” number of additional witnesses and documents; Sen. Mitt Romney (R-Utah.) has said he wants to hear from Bolton; and Sen. Lisa Murkowski (R-Alaska) remains undecided.

Republicans control 53 seats in the Senate and they can afford up to three defections when the Senate votes on the witnesses issue on Friday. 

“If this shallow, hurried and wholly partisan impeachment were to succeed, it would rip the country apart, pouring gasoline on the fire of cultural divisions that already exist,” Alexander said. “It would create the weapon of perpetual impeachment to be used against future presidents whenever the House of Representatives is of a different political party.”

“The framers believed that there should never, ever be a partisan impeachment. That is why the Constitution requires a 2/3 vote of the Senate for conviction. Yet not one House Republican voted for these articles,” he added.

The development came amid calls from Democrats to hear from Bolton after The New York Times reported that he alleged in his forthcoming book that President Trump sought to link U.S. military aid to Ukraine to investigations of Democrats. 

The lead House impeachment manager Adam Schiff (D-Calif.), once said Bolton had a distinct “lack of credibility” and was prone to “conspiracy theories,” claimed that the Senate cannot have a “meaningful” trial without Bolton’s testimony. 

President Trump on Wednesday declared “GAME OVER” as an August 2019 interview of Bolton emerged, showing the former national security adviser called the president’s phone calls with Ukraine’s leader “warm and cordial” and acknowledged that combating “corruption” in Ukraine was a “high priority” for the Trump administration.