Specifically, Ms. Geller said Bannon “articulates what millions of Americans are thinking about how we need to tell the truth about jihad and the Muslim migrant invasion of the West.”

Trump’s open moves toward the alt-right could be effective in renewing the candidate’s focus on Mrs. Clinton. A renewed line of attack on Clinton has the capacity to hurt a vulnerable front-runner who also has historically high unfavorable ratings in polls.

Yet the appointment was disappointing to many establishment Republicans.

By nominating an alt-right darling like Trump to run for president, “the Republican Party has … transformed into the world’s largest and angriest comment section,” South Carolina House minority leader Todd Rutherford (D) told The State newspaper recently.