Republican leaders have given Donald Trump a ferocious pounding over the past week, and have come away with very little to show for their efforts. The Republican front-runner matched or outperformed his polling in the states voting last night, while establishment favorite Marco Rubio saw his support collapse. As anxious anti-Trump eyes turn towards the Republican National Convention in Cleveland, the RNC’s rules are turning against them.

Too much even has been made of Ted Cruz’s victories. So far, he has carried seven states, four of which—Iowa, Alaska, Kansas, and Maine—were caucus states, which he won while receiving only 100,000 votes. These victories are testimony to the strength of Cruz’s ground game in caucus states, not his broad support or his prospects for challenging Trump in the big-state primaries coming up. More significantly, Trump has blown up Cruz’s original strategy for winning the nomination, which depended on sweeping through the southern states on Super Tuesday and building a head of steam going into the big-state primaries. Cruz is left with no path to the nomination unless Trump is denied a majority and the Texas senator prevails in a contested convention.

If Trump fails to win both Florida and Ohio, his opponents could be in position to prevent him from sealing the nomination before the convention. Even if he wins Florida, which now seems likely, but loses Ohio, he might struggle to secure a majority with the full weight of the GOP establishment against him.

One of the singular misjudgments of the 2016 GOP campaign has been the widespread belief that the GOP’s rules give establishment candidates an advantage over the outsiders. This view prevailed into February, but now that a series of establishment favorites have been driven from the race, it’s clear that the delegate allocation rules and frontloading of southern states have favored the outsiders.

Until very recently, pundits and party insiders thought the rules governing the national convention, likewise, favored party insiders. That assumption is now being questioned. The anti-Trump forces will find some of the convention rules useful in their efforts. For example, most states bind delegates to vote for a candidate based on the results of primaries or caucuses in their states. But that obligation extends only through the first ballot. If no candidate wins the nomination on the first ballot, delegates are released and can vote for any nominated candidate. If Trump fails to secure a first-ballot victory, all bets are off. Party leaders would then be in position to broker the nomination of a non-Trump, non-Cruz, maybe even non-candidate, like Paul Ryan—if they can get him nominated.

And there’s the rub. Rule 40(b) of the national convention rules requires a candidate to demonstrate the support of a majority of delegates in eight states in order to have his name placed in nomination. Like other rules adopted at the 2012 convention, Rule 40(b) was designed to tilt the tables in favor of establishment-friendly candidates. With the eight-state rule, GOP leaders sought to avoid floor demonstrations for outsider candidates, such as those who gave Mitt Romney fits through the 2012 primaries. The party wanted to keep the outsiders and their supporters off the stage and out of prime time so that President Romney could be renominated in a show of party unity.

But like the delegate allocation rules, Rule 40(b) has come back to haunt its authors. As things stand today, only Trump seems certain to reach the eight-state threshold. He has already won majorities of delegates in seven states—South Carolina, Alabama, Georgia, Massachusetts, Tennessee, Mississippi, and Hawaii. Cruz, having won majorities in four states—Texas, Kansas, Maine, and Idaho—also has a shot at the threshold.

So, what are the prospects for each candidate to reach the eight-state threshold? The variety of delegate allocation schemes, uncertainty about how many candidates will remain in the race, and the paucity of polling data makes handicapping the race-to-eight a speculative endeavor. But rough assessments of each state suggest how tough it will be for Rubio or Kasich to meet the requirements of Rule 40(b).

As long as votes are divided among three or four candidates, only states with high thresholds and winner-take-all rules are likely to award majorities of delegates to a candidate. These states are:

  • Florida — Winner take all
  • Illinois — Mixed winner take all
  • Missouri — Winner take all above 50 percent, otherwise winner take all by district
  • Northern Mariana Islands – Winner take all
  • Ohio – Winner take all
  • U.S. Virgin Islands — Winner take all
  • Arizona — Winner take all
  • Utah – Caucus with 15 percent threshold
  • Wisconsin — Winner take all statewide and by congressional district
  • New York — Proportional with 20 percent threshold
  • Connecticut — Mixed winner take all
  • Delaware — Winner take all
  • Maryland — Winner take all
  • Pennsylvania — Mixed winner take all
  • Indiana — Winner take all statewide and by congressional district
  • Nebraska — Winner take all
  • Washington — Proportional with 20 percent threshold
  • California — Winner take all statewide and by congressional district
  • Montana — Winner take all
  • New Jersey — Winner take all
  • New Mexico – Proportional with 15 percent threshold
  • South Dakota — Winner take all

Trump needs only one state to reach the eight-state threshold, but he’ll seek more than eight to deny them to his opponents. Based on recent polling, Florida, Ohio, Illinois, Wisconsin, and New York look like opportunities for him. Another four states—Connecticut, Maryland, Rhode Island, and New Jersey—look promising based on their proximity to states where Trump is performing well and older polling data. This gives the New Yorker at least nine states from which he can pick up the one state he needs to meet the eight-state threshold.

Cruz needs four states to reach the threshold. Assessing which states are opportunities is more difficult for him than for Trump because polling data and other information is lacking in these states. But his best opportunities appear to be in Utah, Nebraska, Montana, New Mexico, and South Dakota. Cruz also has opportunities in Guam, Northern Mariana Islands, and American Samoa where he has invested considerable resources, no doubt, with the eight-state threshold in mind. He would need to win majorities in four of these eight states and territories to reach the threshold, so he has a shot.

Kasich needs eight states, and his best opportunity appears to be in Ohio if he can overcome Trump’s lead in the state. Kasich’s prospects elsewhere are difficult to assess until the fallout from Rubio’s (probable) departure from the race takes shape. A three-way race might put California in play for him, but Trump and Cruz are likely to contend for the state, too. In any case, reaching eight states seems like a stretch for Kasich. With Puerto Rico under his belt, Rubio needs seven states, but with his recent collapse and likely defeat in Florida, the question is probably moot.

There’s a caveat to add to this assessment. Approximately 100 unbound delegates are scattered across the states, typically no more than three per state. A candidate who is close to a majority in a state might be pushed above 50 percent with the support of the state’s unbound delegates. Also, three states—Colorado, North Dakota, and Wyoming—do not bind their delegates, so their delegations could produce majorities and throw them in support of one candidate or another.

But all told, the most likely scenario is that only Trump and Cruz will meet the eight-state requirement of Rule 40(b). Kasich might not even come close.

After months of denial, GOP leaders have finally woken up to their Rule 40(b) problem. In theory, this can be fixed before or during the convention. For example, the rule could be changed to lower or eliminate the eight-state threshold. This would require a vote of the full convention. If Trump is short of a majority, his opponents might cooperate to change the rule and allow other candidates to be nominated. However, if both Trump and Cruz have qualified, they’d have the votes and a common interest to block a change in the rule.

But mischief can be made without making changes to Rule 40(b). For example, the rule could be reinterpreted—“support from a majority of a state’s delegates” might be interpreted to mean a candidate can claim a majority by combining the delegates he won in a state with delegates bound to other candidates who have left the race.

Or, a delegate bound to vote for one candidate could “support” the nomination of another candidate without violating Rule 40(b) or any other rule of the convention. The only action a delegate is bound to take is voting for a specific candidate on the first ballot. He or she is not obligated to follow the instructions of any candidate related to any other action that might arise.

Many delegates to the national convention will be party regulars who could be open to cooperating with the stop-Trump forces even if they are bound to vote for Trump. While these delegates must vote for Trump on the first ballot, they are not bound to oppose rule changes that he opposes. If they choose, they could vote for rules that make a first-ballot victory by any candidate more difficult, then vote for Trump on the first ballot. If Trump fails to secure a majority, the delegates would be free on subsequent ballots to support any other candidate who has been nominated. Of course, this would cause pandemonium, but party leaders might prefer a disastrous convention and a Trump third-party bid to a ticket with Trump at the top.

However, if Trump has between 45 percent and 50 percent of the delegates, the convention will probably balk at such machinations. Below 45 percent, and certainly below 40 percent, stop-Trump contingencies could come into play. But if Trump and Cruz, together, hold the lion’s share of delegates, party leaders might find recruiting Cruz to their plan difficult. If Trump has won the majority of states and holds a significant plurality of delegates, Cruz is unlikely to conspire with the party establishment to deny him the nomination. Such an act would violate Cruz’s basic value proposition for his supporters.

More likely, he and Trump would strike a deal. Neither one of them would want to unlock the door and allow party leaders and their loyalists to bring Paul Ryan, Mitt Romney, or any other establishment favorite onto the stage. Instead, Trump will offer Cruz the vice presidency because he knows when it’s time to deal. Besides, it would be one more twist of the knife in the party he and his supporters seem bent on destroying. And Cruz would accept the offer, because he’s ambitious and he’d be one very big step closer to being a heartbeat away from the presidency. Stranger things have happened this election season.

Philip Diehl is a former chief of staff of the U.S. Treasury Department, staff director of the Senate Finance Committee, and director of the U.S. Mint.