Dan Drezner considers the possibility that some Republican policy elites could start moving to the Democrats, but remains skeptical:

The thing is, that polarization has been going on for four decades now. Elites within the major political parties of 2016 are more ideologically distant than they were in, say, 1971. Indeed, this election cycle has exacerbated that polarization at the presidential level. So disaffected GOP intellectuals would have to travel a much longer ideological space to feel comfortable as Democrats.

That doesn’t mean that it couldn’t happen, however. Foreign policy is an issue that’s tougher to fit onto simple left-right axis, so maybe there will be some migration on that front as the GOP nominees sound more rejecionist about the rest of the world.

It’s possible that some foreign policy hawks would vote for Clinton over Trump or Cruz, but in order for many of them to “migrate” to the other party they would have to conclude that most Republicans are flatly rejecting them and their views for the foreseeable future. Maybe they will, but that will take more than one presidential election with a somewhat fluky nominee. It would require their preferred candidates to lose multiple nomination contests, and it would probably also require a Republican nominee they don’t like winning an election and governing in a way they can’t accept. That could end up happening, but that is still a long way off. If this year is the GOP’s equivalent of the Democrats’ 1968, we shouldn’t expect neoconservatives or other policy elites to start abandoning ship for several more years yet.

The big obstacle to switching parties for most foreign policy professionals in the GOP is that they have spent their entire lives portraying the Democratic Party as the party of “weak” and “feckless” foreign policy and radically at odds with what they believe about the U.S. role in the world. As Drezner says, the neoconservatives’ move into the GOP made a certain amount of sense on their terms, and going the other direction would be much harder and more difficult to justify to themselves. In practice, many Republican hawks are much closer to Clinton than they are to some of their party’s own candidates, but they have bent over backwards to claim otherwise for years. It is a measure of how much they loathe Trump (and Cruz to a lesser extent) that some of them are publicly entertaining a vote for Clinton. It doesn’t necessarily suggest a desire to join the other party as anything more than a protest voter. For her part, Clinton doesn’t need the added baggage or headache that would come from embracing the GOP’s failed foreign policy elites, and her own party is already full of liberal hawks that are quite capable of helping her make bad foreign policy decisions without any help from ex-Republicans.

The GOP’s predicament going forward is not that it is likely to lose the policy elites that it already has to the other party. The danger is that younger people interested in policy work will conclude that the party is now so hostile to expertise and so anti-intellectual in its approach to policy that they won’t want to be associated with it in any capacity. The GOP may hang on to its Bush-era policy elites, for all the good that will do them, but if current trends continue it will have an increasingly difficult time getting people from the next generation of scholars and writers to join. That doesn’t bode well for a party that desperately needs to reform its policy agenda.

There was one other bit from the Politico article Drezner cited that stood out to me:

If they scatter, the loss of conservative intellectuals as a somewhat unified force could mean the end of the era of the GOP as the party of ideas [bold mine-DL].

To be blunt, that era ended a while back. If “party of ideas” means being a party of new, relevant, or constructive ideas, the GOP hasn’t been that in at least two decades. Like much of the current Republican agenda, the conceit that it is “the party of ideas” is a holdover from thirty years ago. Even if the party’s current policy elites stay right where they are, the GOP still isn’t going to be a “party of ideas” until it starts adapting its policy agenda to address contemporary problems. That necessary reform is much less likely to happen if the party retains many of the people responsible for its bankrupt foreign policy.