Five states across the northeast are voting in the Republican race on Tuesday, and Donald Trump has long been expected to win all of them. The question is by how large a margin, and whether the shaky alliance between opponents Senator Ted Cruz and Ohio Governor John Kasich can slow him down going forward.
Connecticut, Delaware, Maryland, Rhode Island and Pennsylvania, the five states holding primaries Tuesday, have varying rules for awarding delegates. The most unusual case is Pennsylvania, which gives 17 bound delegates to the statewide winner, but has 54 unbound delegates up for grabs at the Congressional District level.
The campaigns are trying to get supporters to vote for a slate of delegates who favor their candidacy, and many of the delegate candidates say they'll vote for whoever wins their district. It's a key test of organization for Trump, who has proven less than adept at complicated delegate fights, and Cruz sees an opportunity to pick up some delegates.
Trump needs to dominate all of Tuesday's races to stay on pace for the 1,237 delegates he needs to clinch to the nomination. NBC News' political unit sets the bar at 90 to 95 out of the total 118 pledged delegates up for grabs in the five states. Trump also needs two-thirds of Pennsylvania's unbound delegates.
Every delegate matters, because if Trump falls even one delegate short of 1,237 on the first ballot, it will trigger an open convention in which most pledged delegates will be freed to vote for whichever candidate they choose.
So far, Cruz has proven effective at picking favorable delegates while Trump's unpopularity with party stalwarts could make it difficult for him to win in this scenario.
Cruz and Kasich are well aware of this dynamic. Kasich has already been mathematically eliminated from winning with pledged delegates and Cruz will be eliminated on Tuesday.
In order to heighten the odds of a contested convention, the two announced an extraordinary join effort on Sunday to deny Trump 1,237 delegates by dividing up the remaining states. Kasich is withdrawing his campaign from Indiana's May 3 primary, a critical contest where polls show Trump leading Cruz, while Cruz is withdrawing from New Mexico and Oregon.
It's not clear how well it will work, however. For one thing, neither campaign has taken the additional step of urging its voters to support the other candidates in states they've ceded. By contrast, Senator Marco Rubio unilaterally called on his supporters in March to back Kasich in Ohio in order to deny Trump a victory and finished with less than 3% of the vote; although his polling was so weak it's hard to tell if the appeal made a difference.
Cruz did his best to appeal to Kasich voters on strategic grounds on Monday in an appearance in Indiana.
"If you don't want to see Donald Trump as the nominee, if you don't want to see Hillary Clinton as the next president, then I ask you to join us because this is the only campaign that can and will beat Donald Trump and then Hillary Clinton," Cruz said.
Kasich instead portrayed the move as simple matter of shifting campaign funds and staff appropriately.
"This is nothing more than an effort to target my resources, because we're going to a contested convention," he said in a visit to his childhood home of McKees Rock, Pennsylvania on Monday.
Trump dismissed the joint effort as "collusion" and said it made his opponents look "weak" and "pathetic" in speeches in Rhode Island and Pennsylvania on Monday.
"When two candidates who have no path to victory, they have no path to victory, they're mathematically out, they ought to quit so we can all get together, we can all unify, and we can all go against Crooked Hillary Clinton and beat her," Trump told supporters in Wilkes-Barre, Pennsylvania.