EXPLAINER: How can the AP call races right as polls close?

By MIKE CATALINI
Associated Press

The Associated Press could declare winners in some races in this year’s midterm elections at the moment polls close Tuesday. Some are in races with only one candidate on the ballot. And then there are races in which a party or candidate has a past history of consistent and convincing wins. The AP can use results from its survey of the American electorate to decide poll-close calls in these states. That survey is called AP VoteCast and is aimed at determining why voters voted how they did.