As Jonathan and Ilya have recently pointed out, Reason Magazine’s writers are overwhelmingly voting for Gary Johnson, or they are not voting at all.
By contrast, most libertarian law professors of my acquaintance are supporting Romney. (And even back in 2008, when some libertarians supported Obama, this was a distinct minority position among libertarian law professors–though David Post did support Obama on this blog.) Why the difference? One reason, undoubtedly, is that law professors have a much greater than average concern about the Supreme Court. And while one can make the case that a libertarian whose primary concern is gay rights or abortion would prefer a Court with Democratic appointees, here’s something to keep in mind, from a post I wrote back in October 2008:
Libertarians have been heavily involved in some of the most important constitutional Supreme Court litigation of the last two decades, either in terms of bringing the case, being among the most important advocates of one side’s constitutional theory, or both. Among the cases in this category are Lopez, Morrison, Boy Scouts v. Dale, U.S. Term Limits, Grutter, Gratz, Kelo, Raich, Heller, and probably a few more that I’m not thinking of offhand. With the minor exception of Justice Breyers’ vote in Gratz, in each of these cases, the ONLY votes the libertarian side received were from Republican appointees, and all of the Democratic appointees, plus the more liberal Republican appointees, ALWAYS voted against the libertarian side. The latter did so even in cases in which their political preferences were either largely irrelevant (Term Limits), or should have led them to sympathize with the plaintiff (Lopez, Kelo, Raich).
To those examples we can add McDonald, Citizens United, American Tradition Partnership, NFIB v. Sebelius, and, I’m sure, a few others that I’m forgetting.
A broader point is that thanks in part to the “fusionist” (libertarian-conservative) nature of the Federalist Society, and the fact that conservative law professors and other elite conservative lawyers tend to be much more libertarian-leaning than conservative voters or elected officials, libertarians have real influence in conservative, and therefore Republican, legal circles. Richard Epstein and Randy Barnett are “rock stars” on the Federalist Society circuit, and other libertarians, not excluding myself, are frequent guests at Federalist Society events. Libertarian legal books get favorable or at least respectful reviews in conservative venues like the Wall Street Journal, National Review, Commentary, and the Claremont Review of Books. The same books don’t get bad reviews in liberal publications; they simply get ignored. I’ve never heard of a conservative professor objecting to a libertarian potential colleague on ideological grounds, but it happens with some frequency among liberal professors.
In short, for the most part modern liberal legalism doesn’t take libertarian ideas seriously, and when it does it tends to be hostile. Modern legal conservatism, on the other hand, has substantial libertarian influence. Given that the home of modern legal liberalism is the Democratic Party, and the home of modern legal conservatism is the Republican Party, it’s not surprising that libertarian law professors tend to overall prefer the latter, albeit typically as the lesser of two evils.
UPDATE: It’s also worth noting that Republican presidents have occasionally appointed libertarian-leaning judges, from Alex Kozinski to Janice Brown, and others in between, to the federal courts. I can’t think of any similar examples from the Democratic side. Republican-appointed judges have been very friendly to libertarian law clerks (who go on to become law professors). Democratic-appointed judges, not so much. Libertarian law professors who have held high-ranking government positions–Brad Smith, Todd Zywicki, among others–have almost always done so at the instigation of Republicans, not Democrats. And so on.