Nate Cohn: “It’s still early in the primary season, but a whiff of a possible polling error is already in the air. That’s because Donald Trump has underperformed the polls in each of the first three contests.”
“So what’s going on? We can’t say anything definitive based on the data at our disposal, but three theories are worth considering.
”“One of them… seems especially plausible and consistent with something we’ve written about before: Anti-Trump voters are highly motivated to turn out this cycle. It wouldn’t mean the polls will be wrong in November, but it would be good news for Democrats nonetheless.”