If Trump can win both states, he’s on a glide path to earning a majority of delegates ahead of the July 18 convention. The only way to dethrone him at that point would be for the GOP to throw out its existing convention rules. A move that dramatic won’t happen. It would divide and destroy a party that has always prided itself on adhering to rules.

But if Trump doesn’t win both states, the GOP is likely to find itself in Cleveland with no candidate above the 1,237-delegate majority needed to claim the nomination. If that happens, the Republican Party’s own rules lock in a quagmire in Cleveland—and likely a multi-ballot, no-holds-barred convention.

The craziness will unfold in stages, with more delegates increasingly freeing up to vote for whomever they like as the process advances. All that puts a huge premium on an obscure and intricate competition happening right now in each state—the selection of the actual delegates. Any campaign not waging a major, if under-the-national-radar, effort to get its supporters elected as delegates will come up short in Cleveland.

Here’s how just such a chaotic convention could happen.