Unless there’s some eleventh-hour effort being organized by the donor class to go all in on Kasich, hypothetically with Rubio’s backing, I don’t know how else to read this except as a demand to get out of the way and let the party unify behind Trump. Even if it is part of an eleventh-hour play to help Kasich, Cruz and his 30 percent of the vote aren’t going anywhere. A surging Kasich does nothing except guarantee a durable split among anti-Trumpers and Trump’s eventual nomination. To even have a small chance at stopping him, you need a two-man race.

Eh. I’m increasingly convinced that Cruz would fall short even head-to-head with Trump. Rubio’s probably better off at this point sitting out and waiting to endorse Tom Coburn.

Mr. Rubio wants to halt Mr. Trump’s march to the nomination and, despite recently campaigning against each other, is friendly with Mr. Cruz. But in making scores of thank-you calls to donors in recent days, Mr. Rubio has been discouraged by some party financiers from supporting Mr. Cruz, who is reviled by much of the party’s elite, according to a Republican strategist briefed on the calls, who insisted on anonymity to describe private conversations.

If you needed further evidence that at least some members of the establishment would rather do business with the “malleable” Trump than the ideologue Cruz, there you have it. Per Politico, Mike Lee is trying to run an end-around that opposition by convincing Cruz and Rubio to come together on a unity ticket, but not only has Rubio rejected that idea, it remains an open question whether he’ll endorse Cruz at all:

Ted Cruz’s campaign has been exploring the possibility of forming a unity ticket with ex-rival Marco Rubio — going so far as to conduct polling looking into how the two would perform in upcoming primary states…

At the very least, Cruz’s team is hoping for a Rubio endorsement. The two have been in touch since Rubio dropped out last week, and those close to he Florida senator say he’s open to endorsing his Texas colleague — especially if he believes there’s a pathway for Cruz to defeat Trump.

I think he will eventually endorse, although it’s interesting that he didn’t bother to do so this weekend to help make sure Cruz really does get 50 percent in Utah tonight and all 40 of that state’s delegates. Look at it from Rubio’s perspective, though: What does he stand to gain by going all in for Cruz? He’s tired after a long campaign, he’s demoralized, now he’s being asked to help a rival who was supposed to be an unelectable also-ran in the primaries compared to Rubio himself. His prize is if he does this and everything works out is getting to play second banana to Cruz for four or eight years. His punishment if he does this and it doesn’t work out — and it probably won’t — is demonstrating again just how little influence he actually has in his own party. If Rubio joins a unity ticket with Cruz, Cruz might well go on to lose to Trump anyway. It might even be the case that antipathy to Cruz among GOP moderates who liked Rubio runs deep enough that many of them won’t come around to Cruz even after Rubio’s endorsement. Imagine that humiliating headline: “Cruz names Rubio as VP choice; Kasich’s numbers steady.” Given the virtual certainty of a split party after the convention, it’s likely that Cruz would lose badly this fall to Hillary even if he wins the nomination, which would slap Rubio with a “loser” label as he attempts to rebuild his political career. (Then again, Paul Ryan did okay after the 2012 debacle.)

The only reason for Rubio to hop aboard the Cruz train is to make a point about conservative unity against Trumpism. And even there, as I say, he could make the same point by waiting a bit and signing on with Tom Coburn instead. Who knows? Given that Coburn endorsed him in the primaries, we might even see a Coburn/Rubio ticket at some point this year. They’d lose, sure, but everyone expects defeat from a third-party effort. Even having lost, Rubio would be celebrated by conservatives for fighting Trump to the bitter end.

To give you a sense of why he’s hesitating before signing on with Cruz, take a peek at the new national polls this morning. CBS has the race at Trump 46, Cruz 26, Kasich 20; CNN has it Trump 47, Cruz 31, Kasich 17; and Morning Consult has it Trump 45, Cruz 26, Kasich 13. Everyone understands by now that a lingering split among anti-Trumpers means failure; the fact that Kasich’s numbers are in the teens anyway tells you something about disdain among the center of the party for Cruz. Meanwhile, Trump is close to 50, and in only one of those three do Cruz’s and Kasich’s combined totals exceed Trump’s — and even then, they do so by just a point. It’s likely that Trump will win winner-take-all Arizona tonight and quite possible that Cruz will fail to get to 50 percent in Utah, expanding Trump’s overall delegate lead by dozens more. If he wins in Wisconsin in two weeks, plenty of party honchos will start grumbling that Cruz should drop out and say that the party should grudgingly accept its fate and start preparing for Hillary. If you’re Rubio, looking at all that, why would you join a ticket with Cruz? Endorse him and be done with it.