On Super Tuesday afternoon, AP’s Stephen Ohlemacher and Emily Swanson were locked away in a conference room – isolated from their colleagues in the Washington bureau – to review incoming results from AP VoteCast. It was still hours before polls closed, but AP’s survey – developed to be more accurate than traditional exit polling – was already revealing what was about to happen on the biggest night of the Democratic presidential primary campaign.

This was the election day ritual for Ohlemacher, who as AP’s decision editor leads the team of race callers and analysts who will declare winners in more than 14,000 elections this year; and for Swanson, who as director of public opinion research designed the VoteCast survey with the Washington-based polling team. Before any votes are counted, and as voters are still casting ballots, they scour the data from AP VoteCast to try to determine who is going to win.

AP never calls the winner of an election until the last polls are scheduled to close in a given state. In California on Super Tuesday, that was 11 p.m. Eastern. If VoteCast showed either Bernie Sanders or Joe Biden with enough of a lead, it might be possible for the decision team to call the winner as soon as polls closed. The confirmation comes in their analysis of the data.

AP VoteCast found that roughly two-thirds of voters in California didn’t cast a ballot in person on Super Tuesday. Instead, those millions of voters had already put their absentee ballots in the mail before Pete Buttigieg and Amy Klobuchar dropped out the race. By a wide margin, those ballots backed Sanders.

Swanson and Ohlemacher next looked at a unique feature of VoteCast. Among its innovations over in-person exit polling, the survey’s methodology includes interviewing some participants twice – to confirm their vote choice or learn if they’ve changed their minds. Those “recontact” interviews found that Klobuchar and Buttigieg supporters nationwide were moving en masse to vote for Biden.

Except in California. There, Sanders still had a significant edge over the former vice president, even among those who voted on the day of the election. There was little sign the late shift to Biden had significantly eroded Sanders’ margin in the state.

Taken together, it was the evidence Swanson and Ohlemacher needed to conclude Sanders was the winner in California. Their “poll-close call” moved as an APNewsAlert as soon as the clock struck 11 p.m. Eastern, scooping the major U.S. television networks who – relying on traditional exit polls – labeled the race “too early to call.” The New York Times cited AP’s call by name in their headline reporting Sanders’ victory, while the networks relying on exit polls would eventually call the race – more than a week later. 

Of course, the candidate who actually came out ahead on Super Tuesday overall was Biden. And Seth Borenstein was the first to crunch the numbers and prove it.

Borenstein, a science reporter based in Washington, is on temporary assignment to the Decision Desk as AP’s delegate reporter. In the same way that AP calls the winner of elections, AP also uses the vote count to apply party rules and “allocate” delegates to the candidates. Winning states is important for momentum but claiming 1,991 delegates is how a candidate wins the Democratic Party’s presidential nomination.

To allocate delegates, Borenstein had to look far past the overall results. The Democratic Party awards delegates using complex mathematical formulas that vary from state to state, and tiny shifts in vote share can make the difference between a candidate taking home a big pile of delegates – or none at all.

The vote count also doesn’t arrive neatly. County lines don’t often match up with the boundaries of congressional districts. Officials in California only count about a third of the state’s vote on the day of the election in a process that often takes more than a week. For Borenstein, that required days of early mornings, late nights and painstaking analysis of incomplete data to reach this conclusion: Biden won more delegates on Super Tuesday than did Sanders.

Like Ohlemacher and Swanson’s race call, news of Biden’s delegate victory rocketed around the world. As influential Washington newsletter writer Mike Allen noted after Borenstein's delegate scoop, “It’s official: Joe Biden won more delegates on Super Tuesday than Bernie Sanders. AP has allocated more than 92% of delegates, and Biden has a commanding enough lead that Sanders can’t catch up.”

For completing in-depth, accurate analysis of election data on deadline, enabling AP to tell the complete story of Super Tuesday before all others, Swanson, Ohlemacher and Borenstein win AP’s Best of the Week award.