Senate Majority Leader Mitch McConnell abruptly eased his restrictive proposed rules for President Donald Trump’s impeachment trial , backing off the condensed two-day schedule to add a third for opening arguments after protests from senators, including Republicans.

The trial quickly burst into a partisan fight at the Capitol as the president’s lawyers opened arguments Tuesday in support of McConnell’s plan. Democrats objected loudly to McConnell’s initially proposed rules, and some Republicans made their concerns known in private at a GOP lunch.

Without comment, the Republican leader quietly submitted an amended proposal after meeting behind closed doors with his senators as the trial opened. The handwritten changes would a dd the extra day and allow House evidence to be included in the record. There is still deep disagreement about calling additional witnesses.

“It’s time to start with this trial,” said White House Counsel Pat Cipollone, the president’s lead lawyer in brief remarks as the proceedings opened in public.

“It’s a fair process,” he said. “There is absolutely no case.”

Chief Justice John Roberts gaveled open the session, senators having taken an oath last week to do “impartial justice” as jurors. House House prosecutors were on one side, Trump’s team on the other, in the well of the Senatem as senators sat silent at their desks.

Senators were stunned by McConnell’s shift, and aides offered no immediate answers.

But a spokeswoman for Republican Sen. Susan Collins said that she and others had raised concerns. The Maine senator sees the changes as significant improvements, said spokeswoman Annie Clark.

The turnaround was a swift lesson as the White House’s wishes run into the reality of the Senate. The White House wanted a session crammed into a shorter period to both expedite the trial and shift more of the proceedings into late night, according to a person familiar with the matter but unauthorized to discuss it in public.

“READ THE TRANSCRIPTS!” the president tweeted from miles away, as he returned to his hotel at a global leaders conference in Davos, Switzerland. That’s the transcript of his phone call in which he asked new Ukrainian President Volodymyr Zelenskiya for “a favor.” The Democrats cite that transcript as solid evidence against Trump, though he repeatedly describes it as “perfect.”

Democrats had warned that the rules package from Trump’s ally, the Senate GOP leader, could force midnight sessions that would keep most Americans in the dark and create a sham proceeding.

“This is not a process for a fair trial, this is the process for a rigged trial” Rep. Adam Schiff, D-Ca., the chairman of the House Intelligence Committee leading the prosecution, told reporters. He called it a “cover-up.”

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Schiff opened his arguments before the Senate playing a video of Trump calling for more witnesses to testify. Schiff noted the sudden change in proposed rules, made moments before he spoke.

“The facts will come out in the end,” Schiff said. “The question is, will it come out in time? ”

McConnell said, “The president’s lawyers will finally receive a level playing field,” contrasting it with the House impeachment inquiry.

The rare impeachment trial, unfolding in an election year, is testing whether Trump’s actions toward Ukraine warrant removal at the same time that voters are forming their own verdict on his White House.

Just weeks before the first Democratic primary contests, four senators who are also presidential candidates were off the campaign trail, seated as jurors.

“My focus is going to be on impeachment,” Sen. Bernie Sanders, the Vermont independent running for the Democratic nomination, told reporters. He said his supporters would keep working “to defeat the most dangerous president in American history.”

The Democrats say the prospect of middle-of-the-night proceedings, without allowing new witnesses or even the voluminous House records of the trial, would leave the public without crucial information about Trump’s political pressure campaign on Ukraine and the White House’s obstruction of the House impeachment probe.

Rep. Jerry Nadler, the Judiciary Committee Chairman also leading the House team, said: “There’s no trial in this country where you wouldn’t admit relative witnesses.”

Trump’s legal team doesn’t dispute Trump’s actions — that he called the Ukraine president and asked for a “favor” during a July 25 phone call. In fact, the lawyers included the rough transcript of Trump’s conversation as part of its 110-page trial brief submitted ahead of the proceedings.

Instead the lawyers for the president, led Cipollone and a TV-famous legal team including Alan Dershowitz, say the two charges against the president don’t amount to impeachable offenses and Trump committed no crime.

Legal scholars have long insisted the framers of the Constitution provided impeachment as a remedy for “other high crimes and misdemeanors,” a particularly broad definition that doesn’t mean simply specific criminal acts.

Democrats in prosecuting the case against the president point in particular to a General Accountability Office report that found the White House violated federal law by stalling money to Ukraine that had been approved by Congress.

House Democrats, responding Tuesday to arguments by Trump’s legal team, said the president’s legal filing confirmed that “his misconduct is indefensible.”

They wrote, “President Trump’s lengthy brief to the Senate is heavy on rhetoric and procedural grievances, but entirely lacks a legitimate defense of his misconduct.” The president would “rather discuss anything other than what he actually did,” the Democrats wrote.

Roberts administered the oath to one remaining senator, James Inhofe, who was attending a family medical issue in Oklahoma last week when the other senators vowed the oath and signed the oath book.

Also Tuesday, the House Democratic managers overseeing the impeachment case asked Cipollone, the president’s lead lawyer at the trial, to disclose any “first-hand knowledge” he has of the charges against Trump. They said evidence gathered so far indicates that Cipollone is a “material witness” to the allegations at hand.

House Democrats impeached the Republican president last month on two charges: abuse of power by withholding U.S. military aid to Ukraine as he pressed the country to investigate Democratic rival Joe Biden, and obstruction of Congress by refusing to cooperate with their investigation.

No president has ever been removed from office by the Senate. With its 53-47 Republican majority, the Senate is not expected to mount the two-thirds voted needed for conviction. Even if it did, the White House team argues it would be an ”’unconstitutional conviction″ because the articles of impeachment were too broad.