Senate Minority Leader Chuck Schumer (D-NY) vowed Tuesday to force votes for witnesses at the beginning of the upper chamber’s impeachment trial, even though Republicans have the votes to block the demand.

“Make no mistake, on the question of witnesses and documents, Republicans may run but they can’t hide. There will be votes at the beginning on whether to call the four witnesses we’ve proposed and subpoena the documents we’ve identified,” Schumer said in a floor speech. “If every Republican senator votes for a rigged trial that hides the truth, the American people will see that the Republican Senate is part of a large and awful cover-up.”

Earlier Tuesday, Senate Majority Leader Mitch McConnell said he has the votes to quash Schumer’s demand, including the votes of moderates Sens. Lisa Murkowski (R-AK) and Susan Collins (R-ME), who argue the trial should call additional witnesses later in the process — as lawmakers did during then-President Bill Clinton’s trial in 1999.

“I think we need to do what they did the last time they did this unfortunate process and that was to go through a first phase and then they reassessed after that,” Murkowski told reporters on Capitol Hill.

“The process moved to a period during which the Senate debated and voted that three witnesses should be deposed. I believe that this process — the Clinton approach — worked well,” Collins said.

Schumer’s remarks come as John Bolton, former White House national security advisor, has said he is prepared to testify if subpoenaed. In addition to Bolton, Senate Democrats want to hear from acting White House chief of staff Mick Mulvaney; Robert Blair, a top Mulvaney aide, and Office of Management and Budget official Michael Duffey.

“The House has concluded its Constitutional responsibility by adopting Articles of Impeachment related to the Ukraine matter. It now falls to the Senate to fulfill its Constitutional obligation to try impeachments, and it does not appear possible that a final judicial resolution of the still-unanswered Constitutional questions can be obtained before the Senate acts,” Bolton said in a statement. “Accordingly, since my testimony is once again at issue, I have had to resolve the serious competing issues as best I could, based on careful consideration and study. I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify.”

The move by Bolton adds additional pressure on House Speaker Nancy Pelosi (D-CA), who faces ongoing calls to submit two articles of impeachment — abuse of power and obstruction of Congress — to the Senate. Pelosi has failed to transfer the articles since the House approved by of them in a partisan vote last month, claiming those on Schumer’s witness list must be heard to ensure a “fair” trial.

McConnell has called the demand a “non-starter” and a “fantasy.”