It's interesting that the most compelling moment of the Presidential campaign so far involved a face-off between Rudy Giuliani and Ron Paul, because the two men demonstrate just how much two candidates can diverge on policy matters and still both be cast as the "libertarian" in the race. Paul is a libertarian of process and results, you might say: He wants a system of government designed to maximize individual freedom, which to his mind involves a return to lost constitutional principles that strictly circumscribe what the federal government can and cannot do. Giuliani, by contrast, is a libertarian of results alone, and only on certain issues. He wants to maximize "reproductive freedom," for instance, and doesn't care if doing so involves ceding enormous authority to unelected judges; he wants taxes to be low, but doesn't question the principle of income taxation (as Paul does), and so forth. On other issues, meanwhile, he's decidedly authoritarian, which is why it's passing strange to see so many self-described libertarian conservatives - Ryan Sager, for instance - swooning for a guy who has the potential to be Dick Cheney Part II on civil liberties, except with a zest for gun control thrown in.
Passing strange, but perhaps a sign of which face of libertarianism has the broader appeal these days. When the Davids (Boaz and Kirby) at Cato did their analysis of the "libertarian vote", they largely bracketed questions about foreign policy and the national security state, and defined their subjects as voters committed to "economic dynamism and social tolerance" - a description, not coincidentally, that fits Giuliani to a tee. Insofar as there's a constituency for something called "libertarianism," then, it may be a constituency that's comfortable with the sort of libertarianism that Rudy represents, authoritarian tendencies and all. In the world of think tanks and punditry, there are plenty of libertarians (Andrew, for instance) who find Rudy's views on social issues appealing and his views on civil liberties appalling, but I'm not sure there are that many voters who share that consistency. Instead, it seems - at least based on Giuliani's poll numbers compared to Ron Paul's - that a libertarianism that's pro-choice, pro-growth and pro-"enhanced interrogation techniques" is the only libertarianism that has any mass appeal these days.