When an MSNBC interviewer asked David Brat, the economics professor at Randolph-Macon College who toppled Eric Cantor in a primary challenge Tuesday, whether he opposed the minimum wage, he responded on Wednesday, “Um, I don’t have a well-crafted response on that one.”

The political class is billing it as a gaffe. But Mr. Brat’s fellow economists would probably be far more generous.

Assessing the evidence on the effects of the minimum wage is a tricky business, and the evidence isn’t strong enough to support the certainties that pundits seem to demand.

A recent survey of leading economists by the University of Chicago’s Initiative on Global Markets makes the point. The survey asked 38 economists — who run the spectrum from left to right — whether they agreed that “raising the minimum wage to $9 per hour would make it noticeably harder for low-skilled workers to find employment.” Not one of them strongly agreed, and not one strongly disagreed.