NBC News reports that the campaigns of Ted Cruz and Donald Trump are collaborating to deny the nomination to the Republican Party’s third presidential contender, John Kasich.

“I expect the rules committee to require a level of support that would leave only two candidates on the ballot at the convention,” a senior Cruz campaign aide told the news network.

The 112-member committee will literally write the rules for the party’s nominating convention in Cleveland, Ohio this summer.

“The Cruz people and Trump people are fighting hard to make sure their hardcore delegates get on the committee,” said Barry Bennett, a Trump advisor.

Threshold

Rules carried over from the last convention require a candidate to have the support of a majority of the delegates from at least eight states to be considered for the nomination. Cruz might fall short of that threshold, necessitating a rewrite. But it would be in the Texan’s interest to set the bar still high enough for Kasich to be ruled out.

Kasich, the incumbent governor of Ohio, has only won him home state yet. But his delegates — 143 so far — could be decisive in later voting rounds if neither Cruz nor Trump wins outright on the first ballot.

Trump is expected to come closest to the 1,237 delegates needed to win the nomination, even though many in the party fear he would lead them to a crushing defeat against the Democrats’ Hillary Clinton in November.

Cruz is at 463 delegates, by the Associated Press’ count, with 943 still up for grabs. It is possible he could reach 1,237 before the end of the contest, but it is also extremely unlikely.

Contested convention

If neither man reaches 1,237, the convention would go through as many voting rounds as it takes to find a nominee.

Most delegates are only bound to support the candidate who won their state or district on the first ballot. So if Trump were to fall short, his delegates could defect to Cruz or Kasich in subsequent voting rounds.

Kasich would probably be acceptable to most Republicans and polls suggest only he would stand a chance against Clinton in the general election. So it is in Cruz’ interest to keep him off the ballot. That would make him the only palatable choice to regular Republicans who are appalled by Trump.

It is a risky strategy. Taking Kasich out of contention might just give Trump the majority he needs to be elected on the first ballot.

Self-serving

Republicans shouldn’t be surprised that Cruz is willing to risk a Trump candidacy, though. He has shown to be entirely self-serving in his political career so far, from comparing colleagues who refused to support his doomed effort to defund President Barack Obama’s health reforms to Nazi appeasers, suggesting that Chuck Hagel, a Republican defense secretary, received money from North Korea to accusing Arab Christians of not “standing with” Israel even when they did.

If taking the nomination away from Trump would hurt Cruz’ popularity on the far right, he probably won’t.

And if he can block Kasich to improve his own chances of winning, even if it also helps Trump, clearly he will.