The Associated Press reported Monday night that Hillary Clinton is now the presumptive nominee for the Democratic presidential nomination, just one night before the final round of primaries in the 2016 election cycle. Clinton has notoriously led the race ahead of opponent Bernie Sanders since the beginning of the season, in part due to her superdelegate advantage. Now that superdelegate advantage has reportedly pushed Clinton past the 2,383 she needs to become the presumptive nominee. Yet, superdelegates don't really count until their ballots have been cast at the convention. How can Clinton be the nominee already, even with the superdelegate system? It's basically a careful estimation.
The AP essentially calculates the number of delegates committed to each candidate by determining pledged delegates from primary and caucus results and contacting superdelegates to ascertain their endorsements. According to the AP's new report, "a survey of party insiders known as superdelegates shows Clinton with the overall support of the required 2,383 delegates." Most likely, a number of superdelegates who were previously undecided responded to the AP survey and stated their support for Clinton, therefore pushing her over the magic number to trigger the automatic nomination. Of course, the superdelegates have the right to change their mind up until the convention, and the nomination could potentially swing to Sanders during a DNC coup.
But by the same vein, the pledged delegate count is somewhat of an estimation, too — delegates who aren't bound by party rules or state laws could change their votes at the convention and alter the course of the nomination as well. If you extend the hypothetical that far, there's no way to predict what will happen at the convention. The superdelegates count in the estimate the same as the pledged delegates do, because their confirmation to the AP is as valid as the pledged delegates' election at the state party conventions.
The superdelegates are still a very distinct part of the Democratic primary system from the pledged delegates, but they count just as much in determining the presumptive nominee. Although there is always the slim potential for a mass reversal at the convention, the superdelegates' public and private endorsements are as good of a commitment as possible and are ultimately helpful in understanding the future of the race.