From AP, an explanation of just how complicated the Democratic delegate rules are.
By contrast, a Democratic candidate who gains 15 percent of the popular vote in a congressional district generally is guaranteed at least one delegate.
In a race with two equally matched rivals — Obama and Clinton are both running well-funded national campaigns — that tends to leave the winner of the popular vote with only a narrow delegate advantage over a loser who runs a strong race.
Multiply that across dozens of congressional districts — 53 in California — and predicting the winner of the delegate struggle is a virtual impossibility.
Then it gets harder.
For the Democrats, in a congressional district with three delegates, two go to the popular vote winner, and the loser gets the third as long as they win 15 percent of the popular vote.
But in a congressional district with four delegates, the winner and loser in a two-way race are likely to divide the spoils evenly. The winner must receive nearly 63 percent of the vote to get a 3-1 split in delegates, and 85 percent of the vote to win all four.
Then there's the winning by losing scenario.
This can happen in states that award an odd number of delegates in some districts and an even number in others.
Imagine a candidate loses the statewide vote narrowly, but manages to win the districts that have an odd number of delegates.
A version of that happened in Nevada earlier in the year.
There, Clinton had more supporters attend caucuses, but Obama won the delegate contest, 13-12.
