As the nation’s top cop, Sessions would be able to direct limited department resources to pursuing immigration cases. He could launch federal investigations into what he perceives as discrimination against U.S. citizens caused by immigration. He would be in charge of drafting legal rationales for immigration policies under the Trump administration.

And Sessions, as attorney general, could find ways to choke off funding for “sanctuary cities,” where local officials decline to help federal officials identify undocumented immigrants so they can be deported.

Some immigrant advocates are alarmed by the idea of a Justice Department led by someone they see as far outside the mainstream.

“Sen. Sessions’ public statements and history on immigration give [us] real reason to be concerned that his positions, if confirmed as attorney general, would not uphold the values embodied in the Constitution to protect due process and fairness,” said Greg Chen, director of advocacy for the American Immigration Lawyers Association.