Republican presidential front-runner Donald Trump is the only candidate who can win the party’s nomination on the convention’s first ballot. If he stumbles in enough of the remaining primary states and falls short of the 1,237 delegates required to be the nominee, the delegates to the Republican National Convention will choose the party’s standard bearer.

The process that would then play out is governed by dozens of byzantine party rules that determine if, how and when delegates from each state, territory and Washington, D.C., become free to back a candidate other than the one to whom their voters have assigned them.

Before getting into the round-by-round rules of the convention, let's look at who those delegates are supporting. Mr. Trump currently has well over a 400 delegate lead on Sen. Ted Cruz with about 450 delegates remaining.