WASHINGTON — President Trump has often seen the political benefits of stigmatizing Muslims.

During the 2016 campaign, he would not rule out creating a registry of Muslims in the United States. He claimed to have seen “thousands” of Muslims cheering on rooftops in New Jersey after Sept. 11, a statement that was widely debunked. And after the deadly attacks in Paris and California, Mr. Trump called for a moratorium on Muslims traveling to the United States.