As a classical liberal, I regard libertarianism as I would a wilder, younger brother. Libertarianism is younger because it is largely a product of modernity, while classical liberalism is more rooted in the 18th and 19th centuries. It is wilder, because it posits that the public-good function of the state is more limited and the externalities less frequent than I and other classical liberals believe. Yet the philosophies are close kin: they both see that the state poses a perpetual danger to its citizens, only disagreeing at the margin on when it is necessary to relax the strictures on governmental action. And at least with the most sensible libertarians and classical liberals, these disagreements are largely empirical.
Thus, in a race where the Republican candidate for President is careering away from classical liberalism and the Democratic candidate is flirting with the socialist elements of her party, a classical liberal might find a natural home in the Libertarian Party. Sadly, however, the Libertarian ticket has taken some important positions hostile to liberty. Begin with religious freedom.