Three establishment candidates remain standing in the GOP race — Kasich, Rubio, and Bush. Reince Priebus needs two of them to drop out soon, or he and the other GOP establishment pooh-bahs may be faced with Donald Trump winning the GOP nomination with just 30-something percent support of voting Republicans.

How is this possible? The RNC has engineered the primary process to be dominated by winner-take-all contests, presumably to avoid brokered conventions. While the early contests are proportional (with thresholds) in their awarding of delegates, South Carolina is winner-take-all, and starting March 15 (Super Tuesday), virtually all remaining contests are winner-take-all. In all, winner-take-all states add up to well over 900 delegates, well over two-thirds of the 1,237 magic number to win the nomination.

Now, combine the structure of the contests with the fractured-but-persistent establishment slate. Chris Christie has dropped out of that bunch, but his billionaire donor, Kenneth Langone, is now backingJohn Kasich, shoring up the Ohio governor’s chances to stay in the race for a while (Kasich’s home state of Ohio is winner-take-all on March 15). Kasich’s persistence was also energized by his second place finish in New Hampshire.

Likewise, Jeb Bush is not going anywhere even if it remains true that he’s not going anywhere -- he did just well enough in New Hampshire to quell the “give it up” whispers and he has the super PAC money to go the distance. Finally, despite a rough New Hampshire,Marco Rubio is still the RNC’s highest-odds establishment hope.

Kasich, Bush, and Rubio may well be splitting the establishment vote until March 15. The current math says they are splitting 41.9%, as Trump, Cruz, and Carson—non-establishment—are polling at a total of 58.1% (Real Clear Politics average). Trump’s current 31.7% polling average will get some oxygen assuming Ben Carson (6.7%) drops out. With that, a mid- to high-30s average performance by Trump positions him nicely for the winner-take-all contests versus a three-person split of the 42% establishment support that Bush, Rubio, and Kasich (or even a two-person split between two of these candidates) may face.

The alternative to so many winner-take-all contests might be proportional contests all the way to June. That would have virtually guaranteed a brokered convention, but one might guess that the RNC would take that over the Trump (or Cruz?) nomination coming out of a very fractured and persistent field.