There are three ways that Donald Trump still could be denied the Republican nomination.

He could lose the delegate lead: Trump is ahead of Senator Ted Cruz by a little less than 300 delegates. That’s a large advantage, but there are still more than 800 bound delegates remaining to be selected, almost all of them in winner-take-all or winner-take-most states. There isn't enough polling data to indicate what’s going to happen in most of these.

And that delegate lead is a little shakier than it might seem. About 200 delegates are either uncommitted or allocated to candidates who have dropped out of the race. Most of them are free to choose, and there’s reason to believe that most won’t support Trump. Once they declare, Trump's margin could narrow.

There’s an interactive effect, too. If Trump is winning, the free-to-choose delegates will tend to either support him or remain undeclared. If Cruz (or even Governor John Kasich) starts winning, they’ll move in that direction.

If Trump does lose the delegate lead before the convention, it’s extremely unlikely that he could recover to win the nomination.

He could retain the delegate lead, but fail to reach the 1,237 needed to clinch the nomination. If Trump doesn’t win any of the uncommitted or unbound delegates, he needs to win about 60 percent of the remaining bound delegates to get over the top. He’s on pace to fall short by just a few delegates, according to several close observers.

If Trump can’t quite reach 1,237 after the July 7 primaries, he will try to get them during the pre-convention period, the six weeks between the final primaries and the convention.

Party actors who have opposed Trump throughout the primaries will be important players in that scenario. They might fight on, risking a very messy or even downright ugly convention. If most party actors accept Trump as the nominee, it’s likely—though hardly certain—that enough delegates will follow that Trump will get over the hump.

The key questions for party actors at this point are simple: How far from 1,237 Trump remains; what public opinion polls say about both the nomination and the general election; and the extent to which Trump has either reconciled with the party or failed to do so. They might also pay attention to polling on voter preferences about procedure—the new Bloomberg Politics poll has voters preferring the plurality candidate from the primaries over delegates acting on their own—but voters are unlikely to have strong views about procedure, at least if they wind up with a candidate they can support.

He could hit 1,237 and still lose at the convention. It’s not necessarily over even if he appears to have won, though many Republican party actors have signaled that they would consider Trump the legitimate winner if he hit that milestone. That’s because when it comes to the convention, the real players are the delegates and the candidates.

The problem for Trump will be that some of his delegates might be disloyal. That’s because Republican delegate allocation—which candidate gets the votes—is determined in many states separately from delegate selection—choosing the actual people who will make up the Republican National Convention in Cleveland.

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.