Ruler, this is a stats thread. That's it. Your wishes on coverage should be in another thread.
Norse, exit polls show that a good many Hillary supporters also like Obama and would not feel unhappy if he was the nominee. I think the number I saw was 45%. For the Obama supporters, something like 20% would not feel unhappy if Hillary was the nominee. The danger in this primary was the potential alienation of black voters if they felt Obama unjustly lost this nomination. Not so much with any clinton voters
Why are the turnout models off? The likely culprits are that the likely voter model is flawed and that they're not adjusting turnout estimates to account for all the new voters. How were they to know starting off the season that this would happen
Election projection works like this.
First, figure out how certain slices of demographics will vote. Some polling firms slice them up into small groups, others keep them rather large.
Then, use historical records to figure out how those groups typically turn out to vote.
Combine them together and you get projections.