2016 Postmortem
In reply to the discussion: Hillary's Winning the 13-State-Bible-Belt. Sanders is Still Winning the 37-State-Not-The-Bible-Belt! [View all]Attorney in Texas
(3,373 posts)pledging is not necessarily directly tied to popular vote (Sanders likely won the "popular vote" in Iowa, for example, but delegates are not assigned in that manner).
Second, 60% is not a threshold - Sanders could win 58% every remaining contest and he'd win going away; it is true that if he wins only 51% of the delegates in a future contest than he has to do better in another contest to make up for that, but -- by the same token -- when Sanders does better than 57% in a contest (as he will in the next context, Democrats Abroad), then he has credit that will allow him to do worse than his 57% average in another contest.
Finally, I'm not excluding any states. If I had excluded the Bible Belt states, then the OP would have said "Sanders needs to win an average of 49% of the remaining pledged delegates because he's already ahead." The fact that the OP explains Sanders needs to win 57% of the remaining pledged delegates is accounting for Hillary's lead among the Bible Belt delegates.
The only reason Hillary is ahead is because of the way the primary calendar is organized. It was decided long ago to front-load the contest with the former Dixiecrat states with the idea that such a calendar would produce more centrist candidates who would do well in the general election. The thinking behind that calendar is now antiquated, but the lingering results remain - a centrist candidate with ties to the Bible Belt is going to have some built in advantages over a progressive Jewish candidate from New York. If these Bible Belt states switched places on the calendar with the West Coast states, Hillary would be losing right now. The fact that the calendar is set up the way it is creates a false impression that Hillary is doing better than she would if the states were calendared differently.