Close Primary Elections Don't Affect Much

[Garrett78]

36. As you've implied, every primary/caucus being proportional...

...makes overcoming a 200+ delegate deficit quite difficult. It seems to me there are basically 3 paths to the nomination for a person with such a deficit when approximately 3/5ths of the states remain.

1) The candidate who is trailing has to win every small state by a wide margin (so wide, perhaps, that the opponent doesn't meet the threshold for that state), while breaking even in the big states.

2) The candidate consistently wins the small states but not by a large margin, and they win several big states (New York, New Jersey, Ohio and Pennsylvania, for instance) while breaking even in the other big states.

3) The candidate could win really big (by, say, 30+ percentage points) in a delegate-rich state or two (like California and New York), while winning a slim majority of the delegates everywhere else.

I think #1 is Sanders's most viable path, but it seems highly unlikely. #2 is probably the most realistic hypothetical scenario, generally speaking. #3 seems implausible--not just for Sanders, but in general.

On the Republican side of the ledger, however, Trump could be kept from winning a majority of the delegates. Thanks to winner-take-all states, as well as the number of candidates he's running against.

I believe your Michigan percentages are a bit off. Anyway, the fact that Sanders won in spite of being expected to lose badly impacts the narrative. But it doesn't impact the delegate math.