This is where Trump may finally prove to be unlucky in his opponents. Cruz is perhaps the least likely person in politics to give in to the rest of the Republican Party, or to the spirit of the rules, if he can find the votes to fight on. During April and May, Cruz’s campaign will be working hard in every state choosing delegates. If he’s successful, not only will his own delegates be loyal to him, but so will a solid chunk of Trump’s delegates.
Cruz will need those delegates to support him on a vote to “unbind” the delegates—to allow them to vote their preference, ignoring (if they choose) the outcome of the primaries. He also may need their votes for other rules questions, on any credentials challenges (that is, resolving disputes about which delegates were actually chosen).
The process involves three steps. First, the Republican National Committee will establish a set of proposed rules for the convention. Rules maven Josh Putnam says it’s unlikely that those rules will free the delegates. Then, a week before the gathering, those rules will be handed off to the convention’s rules committee, which is free to change them any way it likes. Once that’s done, the rules go to the full convention, which can accept them as is or amend them in any way it deems appropriate.
If the delegates vote to free themselves, then that’s that: They will vote as they wish, regardless of how they were chosen to vote. And presumably, a scenario in which Trump has been allocated a majority of delegates in the primaries and caucuses but loses a floor vote over freeing the delegates, would doom his bid for the nomination.
So voters, party actors or the delegates themselves can still stop Trump. And given how few polls have been published in the remaining states, and how little we know about the actual delegate-selection process, it’s too early to predict whether that will happen.