WASHINGTON — President Joe Biden’s nomination of Adeel Mangi to be a powerful U.S. circuit court judge is in peril after two Senate Democrats announced they will oppose his nomination.

Sens. Catherine Cortez Masto, D-Nev., and Joe Manchin, D-W.Va., have said they will oppose Mangi’s nomination to the U.S. Court of Appeals for the Third Circuit. Democrats holding only a 51 to 49 majority, Mangi’s lack of Republican support means he doesn’t have the simple majority needed to be confirmed. Mangi would be the first Muslim American to serve as a judge on an appellate court, which has the last word on most federal legal disputes.

“Mr. Mangi’s affiliation with the Alliance of Families for Justice is deeply concerning,” Cortez Masto said in a statement to NBC News. “This organization has sponsored a fellowship in the name of Kathy Boudin, a member of the domestic terrorist organization Weather Underground, and advocated for the release of individuals convicted of killing police officers. I cannot support this nominee.”

Mangi has been criticized by Republicans for his involvement in the Rutgers Law School Center for Security, Race, and Rights, with Republicans condemning the center’s decision to host an event on the 20th anniversary of the 9/11 terrorist attacks which featured as a speaker Sami Al-Arian, who pleaded guilty in 2006 to conspiracy to provide services to the Palestinian Islamic Jihad.

Republicans on the Judiciary Committee were criticized for their line of questioning to Mangi during his confirmation hearing regarding Hamas militants’ terrorist attack in Israel, with the White House saying the line of question was driven by Islamophobia.

Manchin said he opposes Mangi because, going forward, he’ll only support judicial nominees that have at least one GOP vote, and currently there are zero who have said they’ll vote for him.

“I don’t think he has any bipartisan support, and I’ve just come to the conclusion I’m not going to continue to go down this path. I believe so strongly in bipartisanship, I believe so strongly in preserving the filibuster, and here we go down this path, lifetime appointments — I just say, enough’s enough,” Manchin told reporters Thursday, saying he would oppose Mangi’s nomination.

But Sen. Lisa Murkowski, R-Alaska, one of the most moderate Republicans, said she hadn’t looked into Mangi and wasn’t ready to take a position.

Murkowski, who isn’t on the Judiciary Committee, said she will base her decision on various factors, including his “judicial experience.” She added that she hasn’t examined the criticism of him. If she ends up backing him, it could give Mangi a lifeline.

Senate Judiciary Committee Ranking Member Lindsey Graham, R-S.C., who has supported many of Biden’s judicial nominees, says he does not see any Republicans voting for Mangi.

“I think they ought to pull this one,” Graham said, “If you look the way I’ve voted, I’ve voted for a high percentage, this is a bridge too far.”

The White House is standing by Mangi, slamming the GOP criticisms as a smear campaign based on his religion. It pointed to the support he has received from the AFL-CIO, the South Asian Bar Association and a GOP-appointed appellate judge.

“President Biden is proud to have nominated Adeel Mangi, whose extraordinary qualifications and integrity are gaining him new backing each day — including from the 7th law enforcement organization to endorse his confirmation, as well as retired circuit Judge Timothy Lewis, who was appointed by President George H.W. Bush. Mr. Mangi, who has lived the American Dream and proven his integrity, is being targeted by a malicious and debunked smear campaign solely because he would make history as the first Muslim to serve as a federal appellate judge,” White House spokesman Andrew Bates said in an email.

“Senate Democrats should side with the qualities that make America exceptional — which Mr. Mangi embodies — not the hateful forces trying to force America into the past,” he said.

The White House also noted Mangi’s written testimony to the committee that he had “no involvement” when asked about the Rutgers Center speaker events featuring controversial people, including one who pleaded guilty to conspiring to provide services to a designated terrorist group.

Senate Minority Leader Mitch McConnell, R-Ky., spoke on the Senate floor about Mangi’s nomination, saying, “We’re told that any questioning Mr. Mangi’s record is Islamophobia.”

“I hope more Democrats will join us in opposing Mr. Mangi,” McConnell said, and not “fall victim to spurious accusations of bias.”

Senate Judiciary Committee Chairman Dick Durbin, D-Ill., has defended Mangi’s nomination, doing so as recently as Thursday morning in response to McConnell’s criticism.

“Let me say at the outset, I think this man has been treated unfairly by the Republicans on the committee and on the floor,” Durbin said Wednesday. “They have made accusations against him, which are unfounded, and I’m afraid they reflect that prejudice against his nomination.”

Durbin said he spoke to Cortez Masto about her opposition.

“I’ve talked to the senator, and I understand her concerns,” he said. “I hope we can provide her with some information for her to reconsider.”

This article was originally published on NBCNews.com