Maybe Donald Trump isn't invincible, after all.

On Saturday, Ted Cruz nuked Trump from orbit in Kansas, pantsed him in Maine, and almost scored coups in the other two states, Kentucky and Louisiana, where he fell short of Trump by just two delegates in the first case and one in the second. Overall, the Texas senator trails Trump in the delegate race by a very manageable 378-295. There's an awfully long way to go to get to the 1,237 needed for the nomination.

It's enough to launch a thousand think pieces on what's become of the GOP's once-unstoppable frontrunner. But perhaps that isn't the big story. After all, Trump's still in the lead. Cruz faces a formidable challenge to beat him outright, even head to head in a cleared-out field.

To my mind, the most fascinating and important aspect of Ted Cruz's Super Saturday is what has become of the GOP's formerly sparkling golden boy, Marco Rubio. The poster child for the party's hopefulness of audacity has simply failed, limping out of Saturday night's matchups with zero wins and 13 delegates. Rubio has now competed in 19 presidential primaries and caucuses. He's lost 18 of them.

As important as it is for Republicans to comprehend why Trump and Cruz have done so well, they could benefit even more from coming to terms with why Rubio has done so poorly. For Trump's support is a mirror image of the party's full court press for Rubio.

From the beginning, Rubio was the face of establishmentarianism today, establishmentarianism tomorrow, and establishmentarianism forever. More Dubya-esque even than Jeb, more chipper than even Lindsey Graham, he was, on paper, the perfect dauphin: Change generations and ethnicities, and pow — no further change needed!

It is this flawed conceit that Republican voters have soundly rejected. But as the Rubio campaign floundered, it swam deeper into the depths. Gone was the candidate's bold but borderline overshare testimony to his faith, replaced by huffy digs at Trump's equipment. Instead of putting meat on the bones of his vaguely plausible yet deeply absurd claim that nothing matters if we're not safe, foreign policy substance was substituted with ever more hyped-up rhetoric — flowery talk of Reaganesque optimism doubly unplugged from the state of the party and the state of the nation.

The post-mortem brigades will do the GOP a disservice if they chalk up Rubio's fade to the quirks of the race or, even worse, to some martyrdom theory. The party, according to some, owes Marco a debt of gratitude for his kamikaze attack on the bully who no one would punch. Certainly it seems, at first blush, they at least should owe him some thanks. On the other hand, it was Rubio's insanely arrogant belief that he was the perfect candidate for 2016 that got the Republicans into this mind-melting mess in the first place. It was Rubio who made Jeb Bush drag out his campaign out of spite, Rubio who took points off of Cruz's board while adding nearly none to his own, and Rubio who lacked the foresight to kick Kasich to the curb and out of his lane.

For all his talent and good intentions, Rubio proved that there's something much worse in this populist season than being born on third and thinking you just hit a triple. However subliminal, his sense of upwardly mobile entitlement was weirdly off-putting and perversely reminiscent of the entitled yes-kid who thinks he should get what he wants because he knows exactly how to give his teachers and school administrators exactly what they want. Rather than embodying the 20th-century Republican story of increase earned through luck and pluck, he became an avatar of the 21st-century striver whose stock in trade is his special snowflakehood.

It remains to be seen whether Rubio can overcome the caricature he encased himself in, accept his loss for what it is, and get out of Ted Cruz's way. Even if he does, there's no clear sign he could find a place beside Cruz on the ticket. With John Kasich polling better against Hillary Clinton, and better able to play copacetic foil to Cruz's stern scold, Rubio's personality as well as his policy are simply not needed on the campaign trail.

Nevertheless, a hard core of party bigs still seem convinced he's essential to the GOP's future. And left to his devices, Rubio will not drop out, before or after Florida. He will become a pawn in a grand yet tawdry game of thrones at the convention — and in so doing, it's safe to say, put the GOP at far greater peril of being split to pieces than anything Trump and Cruz can manage together. Rubio is the face of a wing of the party that acts like the future but is really yesterday's news. And thinks it's full of winners but, so many times already, has decisively lost.

The era of Rubio is over. We live in the age of Trump and Cruz now.