The AP has called winners in elections for more than 170 years. Here’s how it’s done

Associated Press

WASHINGTON (AP) — One question that will be asked over and over again on election night is “Who won?” The Associated Press will answer that question for nearly 5,000 contested races across the United States. Just what goes into determining the winners? A careful and thorough analysis of the latest available vote tallies and a variety of other election data. The ultimate goal is to determine whether there’s any circumstance in which the trailing candidate could catch up. If the answer is no, then the leading candidate has won.