Now, the conventional wisdom is that Paul’s relatively libertarian foreign-policy views are the biggest threat to him in the 2016 GOP primaries. That may indeed be what motivates spending on a barrage of anti-Paul ads in the early states, and perhaps beyond. But losing the social conservative vote in Iowa and South Carolina — either to someone like Ted Cruz or a pure Christian right candidate — is actually Paul’s most immediate obstacle.

Pat Buchanan’s opposition to the Persian Gulf War, far more popular than any intervention Paul has opposed, didn’t keep him from winning the social-conservative vote in 1996. Iowa may have been Ron Paul’s best state among evangelicals in 2012.

But many well-funded conservative candidates have been upended by poorer, less organized candidates to their right on social issues: Pat Robertson over Jack Kemp in 1988; Buchanan over Phil Gramm in 1996; Mike Huckabee over Mitt Romney (if he counts) and Fred Thompson in 2008; Rick Santorum over Rick Perry in 2012.

Each has then gone on to be crushed by the establishment candidate.