Been playing with the numbers, and it's going to be *very* close on whether or not there's a brokered convention. I think the Midwest (and Ted Cruz) is going to be just enough to prevent Trump from clinching. With possibly a huge shout-out to John Kasich and Pennsylvania.
See, there's really only three big blocks of delegates left on the table: New York, California and Pennsylvania.
New York, Trump is polling about 60%, but it's a proportional-by-CD allocation. I have to think there are some Hispanic boroughs in NYC that will break against him, as well as some of the areas around Manhattan. So he'll get a lion's share, but not the full sweep. Kasich will likely be shut out, as there's a 20% threshold.
California is winner-take-all by district (which, because 159 of its 172 delegates are awarded by CD, makes it essentially a proportional election). Cruz would, I think, do well in Northern California and Hispanic areas of Southern California. Trump will win the whiter parts of Southern California. But essentially it'll be about a 60/40 split.
Pennsylvania is winner-take-all, and Kasich is within a couple of points of Trump here. My gut says that Cruz and establishment backers do some strategic voting here and put Kasich over the top, denying Trump any of those 71 delegates.
That leaves him to scrape out delegates wherever he can, and a lot of the remaining states are "Heartland" states where Cruz has been winning.
I think it plays out like this:
4/5:
Wisconsin -- Cruz win
4/19:
New York -- Trump win
4/26:
Connecticut -- split decision (proportional)
Delaware -- Trump win
Maryland -- Trump win
Pennsylvania -- Kasich win
Rhode Island -- split decision (proportional)
5/3:
Indiana -- Trump win (could be a surprise -- if Kasich wins Pennsylvania, he might have enough momentum to carry Indiana. Its also an open primary, s could be a lot of crossover voting.)
5/10:
Nebraska -- Cruz win
West Virginia -- Trump win
5/17:
Oregon -- Cruz win
5/24:
Washington -- Trump win
6/7:
California -- Trump win, but no sweep
New Jersey -- Trump win
Montana -- Cruz win
New Mexico -- Cruz win
South Dakota -- Cruz win
I think at this point, Trump finishes up about 50-100 delegates shy of the nomination. Now, there are some wildcards out there like Colorado, North Dakota and Wyoming, whose delegates are in a weird "vote however the hell you want" status, and if those delegates could make the difference, Trump's campaign will probably promise them all gold-plated blowjobs for life. Which could create controversy all its own if Trump squeaks out a win through "unbounded" delegates who aren't bound to the results of their statewide primary/caucuses.
I think Kasich will drop after 5/3 if he doesn't win Indiana, and may stay on to the convention if he does.
On the other hand, if Trump wins Pennsylvania, that may be enough to knock Kasich out and to put Trump over the top after the 6/7 primaries.