It was clear from the start that neoconservatives would exit the GOP to support Hillary

Kagan is an eloquent writer, but he elides the fact that many of Trump’s positions are not all that different from what the GOP has espoused in the past when it comes to domestic issues. It is on foreign affairs where Trump represents a marked shift and it is this that truly troubles the neocon wing.

Trump has made it clear that he’s dubious about foreign interventions. He’s indicated that he would treat with Russian president Vladimir Putin. His entire foreign policy credo, such as it is, seems to have a Jacksonian pedigree—don’t tread on me.

For its part, neoconservatism has always had a nationalistic streak. But Trump represents everything that the neocons believed that they had purged from the GOP. He represents continuity with the Buchananite wing, the belief that America should tend to its own knitting before launching hopeless wars abroad. When it comes to foreign policy, however, the second generation of neocons such as Kagan does not trace its lineage back to Ohio Senator Robert Taft but to the one that Republicans in the early 1950s reviled: the Truman administration.