The GOP has a Donald Trump problem. Months into the 2016 campaign, he continues to dominate headlines with right-wing vitriol. Meanwhile, credible establishment candidates like Jeb Bush and Marco Rubio have struggled to jumpstart their campaigns.

A recent Washington Post piece suggested that it’s time for the establishment to panic over Trump’s (and Ben Carson’s) campaign. But the article says there is “little appetite for putting a political knife in the back of either Trump or Carson.”

Over the weekend, the Wall Street Journal reported that some GOP appetites are growing. Good for them: A bit of game theory shows why knifing Trump is exactly what the GOP must do.

Game theory applies here because the establishment and Trump have interests that both compete and align. That means each group has an opportunity to act strategically to maximize its advantage.

To see why, consider GOP leaders’ options. They could do nothing and let all candidates continue campaigning into the primaries. Perhaps early voting will thin the herd and send Trump home soon enough for the party to regain political footing.

But that’s risky. If the GOP does nothing, Trump has no incentive to bow out. He’s currently leading some national polls, elevating his own stature and fame. That’s good for Trump. There’s even an outside chance he gets the nomination. That’s great for Trump.

Alternatively, the GOP could wield that political knife. It could pour resources into establishment candidates (say, Bush and Rubio) to elevate their relative stature. At the same time, it could loudly disavow Trump and his rhetoric in the media, exclude him from debates and court donors for the establishment candidates.

The key question is how Trump would respond to each option.

What if the GOP mounts a strong enough campaign against Trump to guarantee he doesn’t get the nomination? Trump could acquiesce and bow out of the race gracefully. But that’s not very…Trump. He would lose his daily headlines and the value they add to his personal brand.

Instead, Trump may well mount a third-party run at the presidency to preserve his spotlight. But that’s an incredibly risky move for the GOP and even for Trump. A third-party candidate would split right-wing votes, making a Democratic victory perilously likely. That’s the disaster scenario for both the GOP and Trump; both prefer any Republican’s policies to any Democrat’s policies.

Given those outcomes, the GOP should act now to mount its campaign against Trump. While Trump and his ilk would hate to be cowed by the establishment, it’s preferable to risking a Democratic victory. Trump, unless hopelessly irrational, would have to step down.

But Trump could also turn this into a winning game of chicken. Chicken is the classic game-theory scenario in which two drivers speed toward each other, each daring the other to swerve – and thereby lose the game. To win at chicken you have to credibly signal to the other driver that you won’t swerve, so that he’ll have to. An extreme strategy is to throw your steering wheel out the window.

Trump could throw the steering wheel out the window right now by vowing to mount a third-party campaign if he doesn’t receive full and fair support from the establishment. Make the threat credible enough and the GOP couldn’t risk the disaster scenario. Party leaders would have no choice but to allow him to sully the next six months of campaign.

That scenario is unlikely. The GOP has already moved first by requiring (and getting) all candidates to sign a ‘loyalty’ pledge. Good for them for understanding the game, but now it’s time to step up and really play. Trump’s rhetoric gets more offensive by the day, actively harming the party. The GOP needs to eliminate its Trump problem before it gets worse.