WASHINGTON (Reuters) – Democratic U.S. senators on Monday sharpened a potential line of attack against Neil Gorsuch’s nomination to the Supreme Court by questioning whether he would be sufficiently independent as a justice in light of President Donald Trump’s vigorous use of unilateral presidential power including his travel ban.

Their comments came after Trump criticized James Robart, the U.S. district court judge who put on hold the Republican president’s Jan. 27 order temporarily barring entry into the United States of people from seven Muslim-majority nations and halting the U.S. refugee program. Trump called Robart a “so-called judge” who made a “ridiculous” decision.

Democrats have expressed worry that Gorsuch, nominated by Trump last week, could act as a rubber stamp for the Republican president’s policies on a nine-seat Supreme Court poised to revert to a conservative majority.

“It’s a serious concern with a president who attacks the judiciary and seems to not respect the rule of law and the Constitution that you have a really independent justice,” Senate Democratic Leader Chuck Schumer of New York, set to meet with Gorsuch on Tuesday, told Reuters.

Gorsuch, continuing a series of private meetings with senators ahead of his Judiciary Committee confirmation hearings, met on Monday with Senator Dianne Feinstein of California, the panel’s top Democrat, at her Senate office.

Afterward, she said Gorsuch is “clearly very smart, caring, and he’s well thought of in Colorado,” where he serves as a federal appeals court judge. But Feinstein said she will make up her mind after the hearing about whether or not to support his confirmation.

“What we would like to see is an independent judge, and the hearing will determine that,” Feinstein told Reuters.

Gorsuch must be confirmed by the Senate to the lifetime post on the high court.

“It’s incumbent upon Judge Gorsuch to make it clear to the American people that he does not believe in ‘so-called judges,’ that he thinks it’s imperative that the judiciary has to be respected as an independent one-third of our government,” said Vermont Senator Bernie Sanders, who unsuccessfully sought the Democratic presidential nomination last year.

“I would look forward to hearing him speak out on that issue,” Sanders added.

Conservative lawyers and Republican senators who are favorable toward Gorsuch cite his record of supporting limited federal powers and his skepticism about courts deferring too much to executive branch interpretations of the law when issuing regulations as signs he would be willing to stand up to Trump.

“I have zero concerns about his independence being compromised,” said Senator John Cornyn of Texas, a Republican who sits on the Judiciary Committee.

Mississippi Senator Roger Wicker, another Republican, said Gorsuch “has a trail of decisions and publications a mile long that suggest how talented he is, that are instructive as to how he would rule on any number of issues.”

With four liberals and four conservatives now on the court, Gorsuch’s confirmation would restore the conservative majority that had existed for decades until the death last year of Justice Antonin Scalia.

Gorsuch’s supporters point in particular to a recent case in which Gorsuch criticized a landmark high court ruling known as Chevron v. Natural Resources Defense Council. That 1984 ruling directed judges nationwide to defer to federal agencies’ interpretation of laws that may be ambiguous.

Gorsuch in a concurring opinion called that doctrine the “elephant in the room” that concentrates federal power “in a way that seems more than a little difficult to square with the Constitution.”

If Gorsuch is confirmed to serve on a court that would have five conservatives and four liberals, Democrats have expressed concern about setbacks for their positions on divisive issues such as abortion, gun control, environmental regulation, and transgender rights.

(Reporting by Lawrence Hurley; Additional reporting by David Morgan and Richard Cowan; Editing by Will Dunham)

IMAGE: U.S. Supreme Court nominee Judge Neil Gorsuch arrives for a meeting with Senator Ted Cruz (R-TX) on Capitol Hill in Washington, U.S., February 2, 2017. REUTERS/Yuri Gripas