WASHINGTON — In an email to constituents, Sen Mitt Romney said Monday he will oppose efforts to decide on witnesses and evidence before opening arguments in the Senate trial of President Donald Trump.

The Utah Republican said he is sticking to the plan outlined in a resolution the Senate will debate Tuesday. Opening arguments in the impeachment trial are anticipated Wednesday.

The plan modeled after the 1999 impeachment trial of President Bill Clinton compresses the proceeding into several days and leaves open the unlikely possibility of a motion to dismiss. It also requires a Senate vote to admit material from House impeachment proceedings.

Romney is among a small group of senators who want the ability to call witnesses following opening arguments and questions by senators to the prosecution and defense teams.

“The organizing resolution released tonight includes this step, and overall, it aligns closely with the rules package approved 100-0 during the Clinton trial,” Romney wrote. “If attempts are made to vote on witnesses prior to opening arguments, I would oppose those efforts.”

Majority Leader Mitch McConnell, R-Ky., has said he has the votes to pass the resolution, but that vote will come after heated debate and attempts to amend it by Democrats who were furious after its release Monday.

Senate Minority Leader Chuck Schumer called the GOP leader’s proposed package a “national disgrace” that amounts to a “cover-up.”

“It’s clear Sen. McConnell is hell-bent on making it much more difficult to get witnesses and documents and intent on rushing the trial through,” Schumer said. He vowed to propose votes Tuesday to try to amend the rules package. He called it a “cover-up.”

A copy of the organizing resolution laying out rules for the third impeachment trial in U.S. history was released hours after Trump’s legal team filed a brief outlining its defense and asked senators to acquit the president “swiftly” of two articles of impeachment accusing him of abuse of power and obstruction of Congress.

Under the resolution, opening arguments would be compressed into four days — two days per side. Then, senators would be allowed up to 16 hours for questions to the prosecution and defense, submitted in writing to Chief Justice John Roberts. That would be followed by four hours of debate. Only then would there be votes on calling other witnesses and new evidence.

At the end of deliberations, the Senate would then vote on each impeachment article.

The rules depart from the Clinton impeachment by requiring a vote for records from the House impeachment proceeding to be admitted into the Senate record.

A senior Republican leadership aide told the New York Times that the change was necessary because the House had denied the president proper due process rights.

A motion to dismiss is allowed under Senate impeachment rules, but Republican senators have said they don’t have the votes for such a motion to pass. There may be enough votes, however, to allow for additional witnesses, which would only require four GOP senators to break ranks.

“There is inevitable political pressure from all sides,” Romney told constituents. “I have spent — and will continue to spend — many hours in careful deliberation about what this process and its potential outcomes could mean for our country.”

A CNN poll released Monday showed a majority (69%) of the public would like to hear from witnesses during the trial. More than half (51%) said said the Senate should convict and remove the president from office, while 45% say the Senate should acquit Trump.

Democrats have framed the debate over witnesses as a question of whether the Senate will conduct a fair trial with all the available evidence.

“If Sen. McConnell prevails and there are no witnesses, it will be the first impeachment trial in history that goes to conclusion without witnesses,” said House Intelligence Committee Chairman Adam Schiff, D-Calif., the lead House manager, Sunday on ABC’s “This Week.”

The tribunal for Trump would not be the first Senate impeachment trial that haggled over witnesses. A similar debate over when and whether to call witnesses in the Clinton trial resulted in the plan McConnell wants to put forward Tuesday. In the Clinton trial, three witnesses were called.

Schumer wants to call four witnesses: Mick Mulvaney, chief of staff; John Bolton, former national security adviser; Robert Blair, senior adviser to Mulvaney; and Michael Duffey, associate director for national security at the Office of Management and Budget.

But Republicans contend that House investigators had their opportunity to call those witnesses and the Senate shouldn’t have to complete the House impeachment probe that GOP senators and the White House contend is a sham political revenge.

Sen. Lindsey Graham, R-S.C., said on Fox News Sunday that the witnesses Schumer requested are protected by executive privilege and won’t testify, although Bolton said he would if subpoenaed. He also warned that if the Senate approves witnesses, they will come from both sides. “There’s not going to be a process where the Democrats get their witnesses and the president gets shut out,” he said.

For his part in the witness debate, Trump tweeted Monday: “They didn’t want John Bolton and others in the House. They were in too much of a rush. Now they want them all in the Senate. Not supposed to be that way!”

The House impeachment case accuses Trump of abusing power by withholding military aid from Ukraine at the same time that the president was seeking an investigation into political rival Joe Biden, and of obstructing Congress by instructing administration officials not to appear for testimony or provide documents, defying congressional subpoenas.

In a 110-page brief filed Monday, Trump’s defense team wrote that the two articles of impeachment brought against the president don’t amount to impeachable offenses and asserts the impeachment inquiry was never about finding the truth.

“Instead, House Democrats were determined from the outset to find some way — any way — to corrupt the extraordinary power of impeachment for use as a political tool to overturn the result of the 2016 election and to interfere in the 2020 election,” the brief stated. “All of that is a dangerous perversion of the Constitution that the Senate should swiftly and roundly condemn.”

The brief is in response to a detailed outline of the House managers’ case that alleges Trump’s attempt to coerce a foreign power to influence the 2020 election poses an ongoing threat to integrity of the electoral process and national security that justifies impeachment.

House managers will file a rebuttal to the White House’s pleading on Tuesday.