Senate Republicans are fuming after Rep. Jerry Nadler accused them on the Senate floor of engaging in a “cover up” to protect the president, seizing on his remarks Wednesday as a significant misstep that they say undercuts Democrats’ impeachment case.

The GOP criticism came as the House impeachment managers, including Nadler, began their opening arguments in the impeachment trial against President Donald Trump on Wednesday, a presentation that could stretch over three days if Democrats use the entire 24 hours allotted to them.

“If the Democrats are smart, they won’t put Jerry Nadler on the field again,” said Sen. Ron Johnson (R-Wis.). “He was so out of line. It’s offensive accusing us of a cover-up.”

“To my Democratic colleagues, you can say what you want about me, but I’m covering up nothing,” added Sen. Lindsey Graham (R-S.C.), a close Trump ally. “I’m exposing your hatred of the president.”

Chief Justice John Roberts admonished both the House impeachment managers and Trump’s defense team early Wednesday after a tense exchange between the two sides on the Senate floor, a reprimand that capped a day of florid speeches by both sides.

Nadler at the time said Republican senators would be taking part in a “cover-up” if they rejected the opportunity to call more witnesses, including former national security adviser John Bolton. Other top Democrats — including Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer — also described the Republican effort not to include witnesses as a “cover-up.”

“I see a lot of senators voting for a cover-up, voting to deny witnesses, an absolutely indefensible vote, obviously a treacherous vote,” Nadler said, as the Senate debated an amendment to subpoena Bolton just after midnight Wednesday.

White House Counsel Pat Cipollone shot back, saying Nadler should be “embarrassed” and demanded he apologize to Trump, with the exchange culminating in Robert’s rebuke.

Johnson and other Republicans described Nadler’s remarks as a significant error that they said would do nothing but alienate GOP senators and maybe even some Democrats, all of whom serve as “jurors” in the trial against Trump.

And Republicans relished the chance to go on offense ahead of the House’s opening arguments, which could last over three days as impeachment managers try one last time to persuade a small band of GOP senators of the need for more witnesses and documents that the White House previously blocked.

“They’ve got a lot of work to do to try to win back over senators. I can tell you that by 2 a.m. last night, people were not happy,” said Sen. Josh Hawley (R-Mo.). “There was open gasping on the Senate floor when Nadler was saying these things. If the goal was to persuade, they took a huge step backward last night.”

Some Democrats privately dismissed the GOP criticism, saying Republicans are only going to vote to acquit Trump anyway, no matter what case the impeachment managers present.

But Democrats were moving quickly to contain the controversy or at least not fan the flames.

Senate Democratic Whip Dick Durbin (D-Ill.) said Roberts’ admonishment was “appropriate.”

“Emotions were running high on both sides and I’m glad that the chief justice addressed both sides,” Durbin said. “We were tired and frustrated with the vote results and I think it showed.”

Senate Minority Leader Chuck Schumer didn’t directly answer a question about Nadler, instead criticizing the White House’s arguments Tuesday, which Democrats have said were riddled with falsehoods, including Cipollone saying Republicans weren’t allowed in the secure area where most of the House impeachment investigation took place.

“The arguments of the president’s lawyers were like a Fox News show, a lot of finger pointing and nothing to do with the actual facts,” Schumer said Wednesday. “If this was an actual trial and you were a jury, after those arguments I’d be certain that the president’s managers would prevail and the president would be convicted.”

And House Intelligence Committee Chairman Adam Schiff (D-Calif.), the lead impeachment manager, tried to defuse the situation ahead of the day’s proceedings, telling reporters that “tempers flare” on both sides, especially after a 13-hour day of dry procedural debate.

“When you schedule a trial as Mitch McConnell did, that’s designed to be hidden in the dead of night, where you require litigants who are going at it for the entire day to go into the wee hours, you’re going to have tempers flare,” Schiff said.

Nadler has made similar comments at press conferences in the run up to the Senate impeachment trial but his remarks on the floor capped what was otherwise a controversy-free day for the team of House prosecutors.

Although he leads the House Judiciary Committee, which has jurisdiction over impeachment, Nadler has been noticeably sidelined at times throughout the House’s impeachment investigation and in the weeks leading up to the Senate trial.

Pelosi appointed Schiff, a close ally, as the lead impeachment manager. Schiff cut off a reporter Wednesday who tried to ask Nadler about the controversy.

“I’m going to respond to the questions,” Schiff told reporters.

But it’s clear Republicans weren’t ready to let the controversy fade, with several GOP lawmakers and aides pouncing on the video exchange between Schiff and reporters and highlighting it on Twitter.

A top aide to Sen. John Cornyn (R-Texas) even circulated the video in a press release under the headline “VIDEO: Schiff vs. Nadler.”

Marianne LeVine and Myah Ward contributed to this report.