What's at stake
There are five states and a territory that will be voting on Tuesday.
In two, Florida and Ohio, the candidate with the most votes gets all of the delegates, 99 and 66 respectively.
In two, Illinois and Missouri, the candidate with the most votes statewide gets all of the statewide delegates -- 12 delegates in each. In Illinois, people in each congressional district elect a three-delegate slate per candidate, giving that person three delegates. If someone hits 50 percent in Missouri, they get all of the state's delegates; otherwise, the winner of each congressional district gets five delegates per win.
In North Carolina, it's simpler: You get one delegate for every 1.39 percent of the statewide vote. (All delegate rules via The Green Papers.)
In total, there are 367 delegates at stake.
Where the race stands
Only recently have there been polls in the states that are voting on Tuesday. The RealClearPolitics average of recent polls gives us a sense of what the voting may look like in three of the biggest states.
Let's apply some rough estimates.
In Florida, Donald Trump seems poised to put the final nail in Marco Rubio's already nearly sealed coffin. Trump leads by double-digits in most polls and, as we noted on Sunday, his support doesn't seem like it's going anywhere. That would allocate 99 delegates to Trump.
In Ohio, John Kasich seems to have take a decent lead. A Quinnipiac University poll released Monday has Trump and Kasich tied, though other polls recently have given Kasich small leads. It's likely that Kasich has got a stronger operation on his home turf than Trump, but it's hard to say what will happen. It seems clear, though, that the state's 66 delegates will go to Kasich or Trump.
In Illinois, Trump has a lead over Ted Cruz. He'll likely win the statewide delegates. But the results of the congressional district elections are less clear. Four years ago, Rick Santorum out-performed Mitt Romney in the more rural western and southern parts of the state, which seems like it might be mirrored by Cruz -- so it's likely that Trump and Cruz will split the rest of the delegates. Meaning something like 51 delegates for Trump and 15 for Cruz.
In North Carolina, recent polls vary. It seems likely that Trump will win the state with at least 40 percent of the vote and that Ted Cruz will be in second with around 30. (This would be consistent with Trump's strong performances throughout the south.) If that happens, we're looking at 29 delegates for Trump and 22 for Cruz -- with the rest divvied up between Kasich and Rubio.
In Missouri, we have very little polling to guide us. Cruz has won its neighbors Kansas, Iowa and Oklahoma, and Trump scored wins in nearby Kentucky, Tennessee and Arkansas. (He also leads in Illinois, as above.) A poll conducted last week showed Trump getting about a third of the vote, just ahead of Cruz -- but that's one poll. If Trump wins the state and he and Cruz split the state's eight congressional seats, east-west, we'd end up with 32 delegates for Trump to 20 for Cruz.
This is a pretty favorable allocation for Trump, taken just after a weekend in which he's gotten a lot of negative press. So he could have moved down -- or up -- and it would be hard to say. (One quick indicator: A Florida poll released Monday shows the events in Chicago may have helped him.)
What the field will look like on Wednesday
But let's go with our estimates. That would give us a field on Wednesday that looks like this:
That's a pretty favorable look at the day's races for Trump -- and if he wins Ohio, he's still precisely 500 delegates short of what he needs. After Tuesday, 500 delegates is more than one-half of all of the delegates that remain.
Of the remaining contests, six -- Arizona, Delaware, Nebraska, Montana, New Jersey and South Dakota -- are winner-take-all, and could give Trump 217 delegates if he wins each state. On top of that, if he keeps edging out the pack in most states, he'll keep getting the most delegates under a proportional allocation system. If he gets 50 percent of all of the proportional delegates, that's 586 in total -- and the nomination. An optimistic road map.
One that assumes a static field. We can assume that Marco Rubio drops out after losing Florida and that Kasich would likely do the same in short order (though it's not clear when that would be). Polling suggests that Trump could lose head-to-head matchups with Cruz -- meaning that instead of pulling away from Cruz, Cruz could pull closer. Cruz would need to win basically every remaining delegate if our estimates above play out, which clearly won't happen.
In other words, the thing to watch on Tuesday is simple and hardly bears isolating: How Trump does at the margins. How many congressional districts he wins. How many delegates he gets in North Carolina. Heck: How many he gets in the Northern Marianas.
Building a successful nomination, Trump is learning, is a bit like building a big, beautiful wall. It requires a lot of time cementing a lot of individual bricks into place. Right now, the path to a contested convention looks more clear than the path to a nominee.