The question facing Senate Republicans, and the entire GOP, is how far they want to hang with the libertarian cool kids. True, the new ideas and energy generated by a high-profile iconoclast such as Paul are something the party sorely needs after last year’s electoral setback left the GOP Senate looking stale and impotent. But that particular brand of ideology, with its intractable belief that nearly all federal government is unnecessary, also carries deep risk—particularly as the party tries to woo minority voters who are more likely to view government activism favorably or retain seniors fearful that their federal benefits will be cut. …

Libertarianism does offer ways for the GOP to broaden its appeal—as nearly every postelection autopsy has deemed necessary—especially among voters turned off by the party’s restrictive social views. It doesn’t consider thwarting gay marriage an imperative, and, as Paul showed in a speech last week, it is amenable to liberal immigration reforms.

But, as Amash might ultimately demonstrate, libertarianism’s fiscal side shrinks the party’s tent. The perception that the GOP favors the rich—something Republican National Committee Chairman Reince Priebus acknowledged last week while unveiling his committee’s blueprint for revival—had a lot to do with the party’s defeat in 2012, as Mitt Romney could attest. Trimming and shelving government programs that help the middle class and the poor risks exacerbating that perception. Moreover, Paul won’t wear the yoke well as a standard-bearer, as shown by his zag on immigration reform this week. His views toward American isolationism and marijuana decriminalization don’t jibe with those of the bulk of his caucus.