Has Hillary Clinton secured the Democratic nomination?

Following Hillary Clinton's victory over her rival Bernie Sanders in the Democratic primary in Puerto Rico on Monday, media outlets such as The Associated Press, The New York Times and The Guardian were quick to suggest she had clinched the presidential nomination.

Does she have it in the bag? Well, it depends on how you count.

At first glance Clinton certainly appears to have a massive lead in party delegates. According to AP's count, she has the support of 2,383 delegates – enough to secure the nomination – while Sanders only has the support of 1,569 delegates.

However, those numbers don't tell the whole story. Of the 2,383 delegates who support Clinton, 571 are "superdelegates" or "unpledged delegates," who unlike "pledged delegates" are free to switch their support to another candidate before voting at the Democratic National Convention in late November. Maybe Sanders hopes some can be persuaded to change their minds if he does well in the upcoming primaries.

This is what happened in 2008, after dozens of superdelegates switched their support from Clinton to then senator Barack Obama when he gained momentum and won a majority of the pledged delegates.

But even if superdelegates aren't counted, at this point Sanders still only has 1,526 delegates – 291 behind Clinton. There are only 714 pledged delegates still up for grabs in the remaining primaries, and they're allocated proportionally in line with the vote.

To catch up with Clinton, Sanders would have to achieve improbably big victories in both California and New Jersey – which due to their large populations have 475 and 126 delegates respectively. In the latest polls Sanders is neck and neck with Clinton in California and behind her in New Jersey.

Therefore it seems unlikely that Sanders could win the nomination by gaining more pledged delegates. His best hope would be for the majority of superdelegates to switch their support from Clinton for some reason – perhaps if something were to upset her campaign or they think Sanders would be the better bet to wın the presidency in November. Right now that looks like a long-shot.

So does Sanders still have a chance?

Probably not – but this has so far been a strange election season, and he's made a habit of defying the odds.