Sen. Lisa Murkowski, a moderate Alaska Republican known for her independent streak, said Wednesday she was “disturbed” by Senate Majority Leader Mitch McConnell’s pledge of “total coordination” with the White House during President Trump’s expected impeachment trial.

In a Christmas Day interview, Murkowski wouldn’t say how she plans to vote at Trump’s trial or whether she believes witnesses should ultimately be called. However, she said McConnell’s comments were just plain wrong.

“In fairness, when I heard that I was disturbed,” Murkowski told Anchorage TV news outlet KTUU. “To me it means that we have to take that step back from being hand in glove with the defense, and so when I heard what Leader McConnell had said, I happened to think that that has further confused the process.”

McConnell, a Kentucky Republican and the most powerful member of the Senate, has suggested he wants to quickly acquit Trump of both articles of impeachment, potentially without allowing a single witness to testify.

Drawing ire from Democrats, McConnell also said earlier this month that he won’t even pretend to be an “impartial juror” at Trump’s trial because he’s in “total coordination” with the White House counsel and “there will be no difference between the president’s position and our position.”

Murkowski suggested McConnell’s comments break with the “impartial justice” oath that all senators must take before an impeachment trial.

“If it means that I am viewed as one who looks openly and critically at every issue in front of me rather than acting as a rubber stamp for my party or my president, I am totally good with that,” Murkowski said.

A spokesman for McConnell did not return a request for comment.

Murkowski’s comments are the first sign of a crack in the GOP’s pro-Trump wall, which has remained rigid despite the president’s attempts to squeeze Ukraine for investigations into his political rivals.

Led by Senate Minority Leader Chuck Schumer of New York, Democrats are putting pressure on McConnell to commit to a trial structure that would include testimony from former national security adviser John Bolton and acting chief of staff Mick Mulvaney as well as subpoenas for Ukraine-related records withheld from House impeachment investigators.

But McConnell has rebuffed Schumer’s requests and says he wants to hold off on locking in any specific plans until Congress returns in January and the trial starts.

Schumer says he wants assurances from McConnell beforehand, arguing that if they wait until the trial, there’s nothing stopping McConnell from going rogue and quickly hosting a vote to acquit the president.

In the event that happens, Schumer could still force full Senate votes on calling individual witnesses.

In such a vote, Schumer would need four Republicans to break ranks to succeed, assuming all 47 Democrats are unified.

Murkowski is one of the Republicans that Democrats are zeroing in on to cross party lines. Other moderate Republicans being targeted include Utah Sen. Mitt Romney, Colorado Sen. Cory Gardner and Maine Sen. Susan Collins.

Spokespeople for Romney, Gardner and Collins did not return requests for comment on Wednesday.