The impeachment trial of President Donald Trump will be the first such trial in U.S. history to feature no witness testimony after Senate Republicans voted on Friday against hearing from any of the firsthand witnesses to the presidents conduct.

Trump was impeached by the House of Representatives on Dec. 18 for withholding congressionally approved military aid from Ukraine in order to pressure the country into investigating a domestic political opponent, former Vice President Joe Biden , and for refusing to cooperate with the Houses investigation into that action.

Senate Republicans blocked efforts to subpoena new witnesses. The 51-49 vote came despite a report on Jan. 26 that former national security adviser John Bolton would write in a forthcoming book that Trump specifically told him that he withheld military aid from Ukraine in order to obtain an investigation into Biden and his son Hunter. Bolton had said he would appear before the Senate to testify if subpoenaed.

But Senate Republicans had already planned to acquit Trump no matter the evidence before them. They refused to hear testimony from Trumps closest aides. Before the trial even began, Senate Majority Leader Mitch McConnell (R-Ky.) said he would not be an impartial juror.

The Senate is now set to acquit Trump in a Wednesday vote.

Trumps impeachment trial is now the only impeachment trial in U.S. history to feature no witnesses. Every previous Senate impeachment trial of a president, federal judge or Cabinet official featured witnesses.

Senate Minority Leader Chuck Schumer (D-N.Y.) said after the vote that America will remember this day as one that the Senate failed to live up to its responsibilities. If the president is acquitted with no witnesses, no documents, the acquittal will have no value, Schumer told reporters. Because Americans will know that this trial was not a real trial.

The failure to call witnesses in Trumps impeachment trial comes after he refused to cooperate with the House impeachment inquiry, an act that led to the article of impeachment charging obstruction of Congress. While previous presidents fought congressional efforts to obtain documents during impeachment investigations, none made such a blanket denial of documents and witnesses as Trump did.

But enough Republicans stood by Trump to get him off the hook, making his acquittal almost certain. Two Republicans, Sen. Susan Collins of Maine and Mitt Romney of Utah, said they would vote to hear from witnesses. But late Thursday, Sen. Lamar Alexander (R-Tenn.), also considered a swing vote, said he would vote against witnesses. Alexander said he didnt need to hear from them to know the bar for impeachment hadnt been met, even though he suggested it was clear Trump did what he was accused of. He said in a statement that it was inappropriate for the president to ask a foreign leader to investigate his political opponent and to withhold United States aid to encourage that investigation. Sen. Lisa Murkowski (R-Alaska), also a swing vote, announced Friday she would oppose calling witnesses. Even if Trump did it, it didnt matter.