Why Haley Probably Is Doing Better in South Carolina Than the Polls Show

It’s common wisdom that Donald Trump will beat Nikki Haley in the South Carolina primary by a hefty margin. There’s no reason yet to doubt that assessment. Public polling nonetheless likely will have a systematic pro-Trump bias that observers should account for.

This bias comes from the inherent difficulty of polling in a party primary that, in the case of South Carolina’s and others’, is not limited to voters registered in that party. Pollsters’ work is only as good as the accuracy of their samples. If the sample to interview with is not representative of the actual electorate, their results will be off.