Trump’s base has shown that it is invigorated by challenges to the president, whether they come from Democrats or Republicans seen as part of the GOP establishment.

And Trump has generally emerged from intra-GOP conflicts with strength.

Unlike George H.W. Bush or Ford, Trump’s standing with the GOP base is strong. His approval rating in the GOP hovers around 90 percent.

Republican strategist Ford O’Connell said a primary challenge doesn’t scare Trump because “nobody energizes the GOP base more than Donald J. Trump.”