They used an advanced algorithm called counting:
AP concluded that Hillary Clinton had enough delegates to clinch the nomination after a painstaking but very straightforward exercise.
By Monday evening, 571 superdelegates had told us unequivocally that they intend to vote for Clinton at the convention. Adding that number to the delegates awarded to Clinton in primary and caucus voting to date gave her the number needed to be the presumptive nominee.
That is news, and reporting the news is what we do.
Don’t get me wrong. I like Bernie as much as I can like a politician. But it’s just kind of ridiculous at this point that he thinks he has a shot of being the Democratic nominee. Hillary at the moment has over 3 million more votes than he does (and is destroying him where it counts, the delegates). People seem to be forgetting that when Clinton conceded in 2008, her and Obama were virtually tied in the popular vote and the delegate counts were very tight.
It’s an emblematically annoying ending to the Democratic campaign, one that reflects both the acrimony between Hillary Clinton and Bernie Sanders and the fact that Clinton, in the end, is winning her party’s nomination by every available measure.
At 8:20 p.m. EDT on Monday night, The Associated Press declared Clinton to be the presumptive Democratic nominee based on her having accumulated 1,812 elected (pledged) delegates and 571 superdelegates, for 2,383 total delegates, exactly the number needed to win the nomination. In the overwhelming likelihood that Clinton’s nomination is confirmed at the Democratic convention in Philadelphia next month, she will officially become the first woman nominated for president by a major American political party.
In a statement released after the AP’s call, the Sanders campaign argued that the media is wrong to declare Clinton the presumptive nominee by including superdelegates, correctly pointing out that superdelegates can change their vote up until the convention, as several dozen superdelegates did in flipping from Clinton to Barack Obama in 2008. FiveThirtyEight’s pledged delegate count, which does not include superdelegates, has Clinton with 1,8111 pledged delegates to 1,526 for Sanders. The Sanders campaign said its “job from now until the convention is to convince superdelegates that Bernie is by far the strongest candidate against Donald Trump.”
But Sanders’s statement — and the AP’s call — distract from the larger point. Clinton will be the Democratic nominee because substantially more Democrats have voted for her. In addition to her elected delegate majority, she’s received approximately 13.5 million votes so far in primaries and caucuses, compared with 10.5 million for Sanders.
But there could be an explanation: