As with Cantor, plenty of other factors played a role in the Georgia runoff. (Most postmortems on the race focused on Perdue’s appeal as a political outsider, and Kingston’s status as a 22-year member of Congress, in a political climate seen as hostile to Washington.) But given the closeness of the result, the late-breaking amnesty attack may well have pushed Perdue over the top. If so, it would be the second time this year that Republican base voters have risen up against a candidate seen as sympathetic to the business community’s desire for immigration reform.

In the past, contrary to popular belief, support for immigration reform has seldom been toxic in Republican primaries. (A notable exception came four years ago in Georgia, when Nathan Deal ran to the right on immigration on the way to winning his gubernatorial primary and the governorship.) But the current crisis on the border has inflamed the perpetual hot-button issue, particularly among the vocal minority of the Republican base for whom the only acceptable “reform” is mass deportation. And candidates like Perdue are exploiting the issue as a wedge.