Jeff Roe, Cruz’s campaign manager, tweeted Saturday night after the release of the Register survey that Selzer’s poll was making assumptions about turnout that were unlikely to be borne out. Roe pointed out that the poll interviewed 3,019 registered voters – 602 of whom were determined to be likely to attend a Republican caucus.

Roe’s tweet: “602/3019 GOP voters is 19.9% of the 1.9 active voters in the state; simple math says: 386,000 turnout for GOP #youhadonejob.”

But all registered voters isn’t necessarily equivalent to those registered voters who would participate in a poll. Studies show that voters who are more likely to take the time to answer pollsters’ questions are also more likely to turn out for an election.