Clinton has 1.821 pledged delegates but the AP said she reached the 2.383 delegates needed to become the presumptive Democratic nominee with a weekend victory in Puerto Rico and late burst of support from superdelegates. Those are party officials and officeholders, many of them eager to wrap up the primary, free to support whichever candidate they want.

However, the Sanders campaign questions the tally. A spokesman called the move to declare a presumptive nominee a “rush to judgment”. Speaking to MSNBC on Monday evening, Michael Briggs said superdelegates can and had changed their minds in previous contests. This would also be the case when Barack Obama run against Hillary Clinton.
 
“It counts superdelegates that the Democratic National Committee itself says should not be counted because they haven't voted and won't vote until the summer” Briggs told the show.
 
Sanders campaign now seeks to convince senior Democrats that he is the best candidate to defeat Donald Trump in the United States election in November.
 
Also, supporters of Bernie Sanders argue that the timing of the announcement before a crunch primary in California on Tuesday adversely affects their candidate's chances of winning the state. 
 
Even though Clinton said she would not “get ahead of herself” it is highly unlikely Sanders will manage to win the nomination. Clinton is in fact ahead with pledged delegates, independently of superdelegates.
 
Clinton touted the news at a campaign event, saying the campaign is now on the “brink of a historic … unprecedented moment”. But even she stressed that six states are yet to vote on Tuesday.