And then there were three. With the departure of Marco Rubio from the race after his defeat in Florida, the competition for the votes of those opposed to Donald Trump is now limited to Ted Cruz and John Kasich. That number might have been reduced to two had Kasich not won a strong victory in his home state of Ohio on Tuesday. The governor’s win was good news for the stop Trump movement, since it denied all of the state’s 66 delegates to the frontrunner. Had Trump won Ohio, his odds of winning the 1,237 needed for the majority would have been greatly increased. But it’s also bad news for Trump’s opponents because it means he can go on winning primaries with less than 50 percent of the vote. That will be crucial in the coming two months with more winner-take-all states that will fall into his lap if Cruz and Kasich continue to compete with each other.

That leaves the two remaining alternatives to Trump with a choice. They can informally unite and choose not to compete against each other in the states where either has the better chance to win. Or they can go on fighting each other and transform Trump from the likely nominee to the certain winner of the GOP contest.

Can Cruz and Kasich cooperate enough to block Trump from getting a majority of the delegates before the Republican convention this summer?

In theory, the answer is yes. Trump will have to win nearly 60 percent of all the delegates left to be won after Tuesday night in order to get to the magic number, and that won’t be easy. The mix of states that award delegates on a proportional basis is enough to put pressure on Trump to win all or most of the winner-take-all states like Pennsylvania and New Jersey. But as we’ve seen over the past several weeks, so long as Trump is competing against multiple opponents, he’s likely to win pluralities even if the majority of voters tell us they don’t want him to be their party’s nominee.

Faced with this dilemma, the choice seems obvious. Cruz and Kasich have to enter into some kind of alliance, whether formal or informal and divide up the map between them. That would mean Kasich agreeing not to campaign in states where Cruz is the obvious alternative to Trump — like Arizona, North Dakota, or Nebraska — and to ask his supporters to vote for the Texas senator. It would also require Cruz to do the same in states like Pennsylvania and New York, where Kasich’s more moderate stance will probably make him more electable.

Unfortunately for those hoping against hope that Trump can be denied the nomination, this isn’t likely to happen. Why?

The first reason has to do with pride and ego and the conceit of both candidates and their campaigns.

Cruz genuinely believes he is the only viable alternative to Trump, and if we think only in terms of the current delegate math he’s right about that. Kasich has no path to the nomination so, in Cruz’s view, the only rational thing for the Ohio governor to do is for him to withdraw now that he’s prevented Trump from winning the Buckeye State. Cruz is also convinced that he can win a one-on-one battle against Trump anywhere in the country even if that probably isn’t true in states where his religious conservatism and Tea Party sympathies aren’t likely to gain as much support as Kasich’s recycled compassionate conservatism.

But Cruz is not the only one here with an outsized ego. Kasich may understand that it is mathematically impossible for him to get to 1,237 even if he won every remaining primary. Yet he is determined to go on competing with Trump everywhere he can because he thinks his brand of Republicanism is what the voters want. The fact that this belief has been debunked everywhere but in a state where he is a favorite son isn’t something he appears to be ready to accept. Neither man seems to be flexible or wise enough to make an alliance rather than sticking to a solo run whose sole purpose may wind up being to secure the title of runner-up rather than stopping Trump.

The truth is, the non-Trumps should have already been cooperating, but none of them has been able to be big enough to admit that they can’t win every state. The only candidate to make such statement was Rubio, who urged his supporters to back Kasich in Ohio. But neither Kasich nor Cruz returned the favor in Florida where Rubio was clearly the closest to Trump in the polls. That doomed Rubio and reduced the ranks of the field by one. But it also guaranteed that Trump would win all 99 Florida delegates.

The other problem is that even if the two men were inclined to cooperate there’s no obvious mechanism or formula for them to determine which states they’d each stay out of. Both can make cases for their chances in states like Indiana and Wisconsin. Other prizes are so tempting — like the greatest one of them all in California — that it will be almost impossible for either to stay away.

But the third problem with a Cruz-Kasich alliance is that there is no guarantee that the non-Trump in any given state will beat the Donald. To date, Trump’s support has been kept below the 50 percent mark everywhere enabling his competitors to point out that most Republicans haven’t voted for him. But rather than stay at the 30-40 percent “ceiling” that most of us assumed he’d be held below, Trump’s numbers have continued to rise as the field shrank. With Trump now consistently getting at least close to 40 percent of the vote — as he did in all five primaries on Tuesday night — there’s no assurance that he has any sort of ceiling even against a single opponent. And the closer he gets to the nomination, the more voters may decide to jump on his bandwagon even if they have misgivings about his personality and his positions.

There’s time for Cruz and Kasich to work out an informal pact that really could stop Trump from arriving in Cleveland with the delegates he needs. But the obstacles to such a deal are great. Though most pundits are saying that Ohio will mean that Trump can’t win an outright majority before the convention, his very strong performance everywhere else may tell us that it’s time to accept the fact that he is going to be the GOP nominee. Indeed, with or without a Cruz-Kasich deal, Trump may be in better position to get to 1,237 than most people think.

The non-Trumps should have already joined forces before Tuesday. It may now be too late for them to do so successfully. But it may also be impossible.