Where are libertarians going? What is clear is where they are not going. The much-touted "libertarian moment," as a New York Times Magazine article phrased it two years ago, never materialized. The story hailed the presidential aspirations of Sen. Rand Paul (R-Ky.) as the harbinger of a political sea change that would usher in a new era for the GOP and the country. It never happened. What happened instead was Donald Trump.

Throughout his presidential campaign, Senator Paul spent much of his energy backtracking and distancing himself from the strict libertarian positions of his father, former congressman Ron Paul, particularly on foreign policy. Team Rand thought they had only to trim their sails and he would enter the GOP mainstream: instead, the ship capsized and sank.

As the senator caviled and maneuvered in a bid to look respectable, Trump did precisely the opposite: defying the political class, he launched a frontal assault on the GOP establishment—and succeeded in overthrowing it, to the cheers of the Republican grassroots.