How Anti-Immigration Passion Was Inflamed From the Fringe

In January 2015, when few were watching, Mr. Sessions wrote a 23-page memo that predicted that the next president would most likely be a Republican who spoke to the working class about how immigrants had stolen their jobs.

.. Most mainstream politicians ignored the memo, but its contents influenced Mr. Trump. At a raucous 2015 rally in Mobile, Ala., he sensed the power of the immigration issue as a crowd of 30,000 supporters roared with approval at his promise to build a wall across the southern border and crack down on illegal immigration.

.. By then Mr. Sessions and Mr. Miller were the architects of the immigration agenda of the long-shot Trump campaign. In 2016, Mr. Sessions endorsed Mr. Trump for president — his first ever endorsement of a candidate in a primary — and Mr. Miller did as well.

.. Both men have something else in common: They are largely unfazed by criticism or bad press.

Mr. Sessions is known for proudly holding opinions thought to be retrograde. Under his high school yearbook photo was the caption: “He is a host of debaters in himself.” While serving as Alabama’s attorney general, he supported reviving chain gangs of volunteer inmates and tighter identification requirements for Alabama voters.

.. Mr. Miller is similarly immune to critiques from establishment Republicans, who often view his immigration positions as far out of the mainstream and politically dangerous. In the recent interview, Mr. Miller dismissed as ignorant the hand-wringing of Republicans about the family separation controversy.

.. “You have one party that’s in favor of open borders, and you have one party that wants to secure the border,” Mr. Miller said. “And all day long the American people are going to side with the party that wants to secure the border. And not by a little bit. Not 55-45. 60-40. 70-30. 80-20. I’m talking 90-10 on that.”

.. Mr. Sessions urged lawmakers to pass legislation to build a wall along the southern border and impose new restrictions on immigration that he said would end legal “loopholes” that let illegal immigrants in.

“If we build the wall, if we pass legislation to end the lawlessness,” Mr. Sessions said, “we won’t face these terrible choices.”