At the prediction market Betfair on Friday morning, bettors put Donald Trump’s chances of winning the Republican presidential nomination at 56 percent. That’s down a fair bit — Trump had been hovering at about 70 percent after his win in Arizona (and loss in Utah) last week. Meanwhile, the likelihood of a contested convention according to bettors has considerably increased. There’s now a 63 percent chance that the convention in Cleveland will require multiple ballots, according to Betfair.

In other words, the markets are now betting on a contested convention. Not just a near-miss, where the nomination is resolved at some point between the last day of GOP primaries June 7 and the start of the convention July 18, but the thing that political journalists dream about: a full-blown contested convention where it takes multiple ballots to determine the Republican nominee.

Here’s the thing, though: Those markets don’t make a lot of sense. If you really think the chance of a multi-ballot convention is 63 percent, but also still have Trump with a 56 percent chance of winning the nomination, that implies there’s a fairly good chance that Trump will win if voting goes beyond the first ballot. That’s probably wrong. If Trump doesn’t win on the first ballot, he’s probably screwed.

The basic reason is simple. Most of the 2,472 delegates with a vote in Cleveland probably aren’t going to like Trump.

Let’s back up a bit. In most of our discussions about delegates here at FiveThirtyEight, we treat them as though they’re some sort of statistical unit. We might say a candidate “racked up 44 delegates” in the same way we’d say Steph Curry scored 44 points. But those delegates aren’t just a scoring mechanism: Delegates are people, my friends. Delegates are people!

And as I said, they’re mostly people who aren’t going to like Trump, at least if the excellent reporting from Politico and other news organizations is right. (If Trump turns out to have more support among GOP delegates than this reporting suggests, even marginally, that could end up mattering a great deal.) How can that be? In most states, the process to select the men and women who will serve as delegates is separate from presidential balloting. In Massachusetts, for instance, Trump won 49 percent of the GOP vote on March 1 — his highest share in any state to date — to earn 22 of the state’s 42 delegates. But the people who will serve as delegates haven’t been chosen yet. That will happen at a series of congressional district conventions later this month and then a Republican state meeting in May or June. According to Politico, most of those delegates are liable to favor Ted Cruz or John Kasich rather than Trump. Twenty-two of them will still be bound to Trump on the first ballot, but they can switch after that. The same story holds in a lot of other states: in Georgia, Louisiana and South Carolina, for instance — also states that Trump won.

Trump’s delegate problems stem from two major issues. One is his lack of organization: Trump just recently hired a strategist to oversee his delegate-selection efforts; Cruz has been working on the process for months. The other is his lack of support from “party elites.” The people who attend state caucuses and conventions are mostly dyed-in-the-wool Republican regulars and insiders, a group that is vigorously opposed to Trump. Furthermore, some delegate slots are automatically given to party leaders and elected officials, another group that strongly opposes Trump, as evident in his lack of endorsements among them.

There are various ways these delegates could cause problems for Trump. The most obvious, as I mentioned, is if the convention goes to a second ballot because no candidate wins a majority on the first. Not all delegates become free instantaneously, but most do, and left to vote their personal preference, most of them will probably oppose Trump.

Conversely, Trump isn’t totally safe even if he locks up 1,237 delegates by the time the final Republicans vote. The delegates have a lot of power, both on the convention floor and in the various rules and credentials committees that will begin meeting before the convention officially begins. If they wanted to, the delegates could deploy a “nuclear option” on Trump and vote to unbind themselves on the first ballot, a strategy Ted Kennedy unsuccessfully pursued against Jimmy Carter in 1980.

Although I’d place fairly long odds against this thermonuclear tactic, there’s also the possibility of piecemeal skirmishes for delegates. In South Carolina, for instance, delegates might unbind themselves on the pretext that Trump withdrew his pledge to support the Republican nominee. Remember those chaotic Nevada caucuses that Trump won? They could be the subject of a credentials challenge. There could also be disputes over the disposition of delegates from Marco Rubio and other candidates who have dropped out of the race. A final possibility is “faithless delegates,” where individual delegates simply decline to vote for Trump despite being bound to do so by party rules. It’s not clear whether this is allowed under Republican rules, but it’s also not clear what the enforcement mechanism would be.

I don’t want to make too much of these “nuclear” possibilities, given that such efforts would be blatantly undemocratic and would risk a huge backlash from Republican voters. Still, even 1,237 delegates isn’t quite a safe number for Trump, especially if he’s just barely above that threshold.

Another possibility is Trump coming up somewhat short of 1,237 delegates, but close enough that he could win on the basis of uncommitted delegates who vote for him on the first ballot. In fact, Trump finishing with something like 1,200 delegates is a strong possibility. The expert panel we convened two weeks ago had Trump finishing at 1,208 delegates — with a lot of uncertainty on either side of that estimate — and he’s run just slightly behind our projected pace since then by getting shut out of delegates in Utah.

Let’s say that Trump ends with exactly 1,200 delegates after California. He’d then need 37 uncommitted delegates to win on the first ballot. That might not seem like such a tall order — there will be at least 138 uncommitted delegates, according to Daniel Nichanian’s tracking, and Trump would need only 27 percent of those. But most of those delegates are chosen at state meetings and conventions, the same events producing unfavorable delegate slates for Trump in Massachusetts and other states.

Alternatively, Trump could try to broker a deal with another candidate — Kasich, for example — to get to 1,237. But that isn’t so easy either; whether Kasich could instruct his delegates to vote for Trump on the first ballot would vary depending on the rules in each state, and some delegates could become unbound instead of having to vote Trump. Trump and Kasich could also try to strike a deal on the second ballot — but by that point, most of their delegates would have become free to vote as they please.

This is not an exhaustive list of complications. We’ll save the discussion about Rule 40 — and why it’s largely toothless — for another time, for instance. The basic problem for Trump is that all the rules will be written and interpreted by the delegates, delegates who mostly don’t like Trump. They have a lot of power to wield at their discretion.

That’s not to say the rest of the voting doesn’t matter — it would be much easier, both procedurally and ethically, to block Trump from getting the nomination if he comes into the convention with 1,100 delegates instead of 1,300.

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