Washington • Sen. Jeff Flake said this week he would oppose the nomination of Utahn Ronald Mortensen for a top State Department job overseeing refugees because of his past rhetoric against immigrants, becoming the first Republican senator to publicly balk at President Donald Trump’s pick.

Flake, an Arizona Mormon who is not seeking re-election, tweeted Tuesday night, “This nominee will not have my support.”

His office didn’t immediately respond to a question about why Flake staked out his position.

Utah’s senators, Orrin Hatch and Mike Lee, have not said whether they’d back Mortensen, a former foreign service officer who has been highly critical of undocumented immigrants, linking them to higher rates of crime and disease.

Republicans hold a one-seat majority on the Senate Foreign Relations Committee, which will consider Mortensen’s nomination. (Neither of Utah’s senators sits on the panel.)

Democrats are likely to oppose Mortensen, meaning Flake’s position could put the nomination at risk or possibly sink it if another GOP senator comes out against Trump’s choice.

Sen. Bob Menendez of New Jersey, the top Democrat on the committee, raised questions about Mortensen’s past rhetoric and his fellowship with the Center for Immigration Studies, which the Southern Poverty Law Center has called a hate group. That concern could spread to Menendez’s fellow Democrats.

I am deeply concerned with Mr. Mortensen’s deep involvement with some of our nation’s most anti-immigrant organizations, and I find some of his past statements not only offensive and inaccurate but fundamentally in contradiction of American values and history,” Menendez said in a statement. “The United States has always been a beacon of freedom and liberty for those fleeing violence and oppression. Our acceptance of refugees and our refugee policy are not just moral imperatives but play a critical role in best positioning the United States to achieve our own foreign policy objectives and build international consensus.

At a time when our nation’s immigrant community finds itself under full assault by President Trump’s nativist agenda, we must reject any attempt to elevate anyone who has promoted hateful, bigoted rhetoric and radical ideas to such a powerful role,” Menendez continued.

Mortensen has referred questions about his nomination to the State Department, which punted them to the White House.

The Trump administration hadn’t responded to questions about Mortensen’s anti-immigrant rhetoric but noted that he’s worked for the U.S. Agency for International Development’s foreign disaster program and previously served as a diplomat in France, Australia, Canada, Gabon, Mauritania and Chad. He had worked on humanitarian efforts that saved lives and alleviated the suffering of millions of people, the White House added.

The ACLU, Southern Poverty Law Center and others have raised concerns as well about Mortensen’s nomination.

Fwd.us, a bipartisan group advocating for immigration reform led by Facebook founder Mark Zuckerberg and other Silicon Valley entrepreneurs, called on senators to examine Mortensen’s “incredibly disturbing record very closely” and vote against him.

His nomination is part of a very deliberate policy agenda by this administration to radically restrict legal immigration and deter others from immigrating to the United States,” the group’s president, Todd Schulte, said in a statement. “The Senate’s job is to advise and consent on key nominations, and it’s clear from Mortensen’s track record that he is unfit to serve in government.”

Rep. John Curtis, a Utah Republican facing a primary race against Chris Herrod, said in a debate Tuesday that he was disturbed by what he was hearing about Mortensen and although he doesn’t have a vote in the House on nominations, he would oppose him if what has been reported is true.

There is no way that this congressman will ever vote for a racist to fill that position,” Curtis said.