DETROIT -- The Republican debate in Detroit just ended, and the battle lines in the partys civil war are now clearer than ever.

On one side are Marco Rubio and Ted Cruz, Mitt Romney and the Republican leadership in Washington, Fox News and most of the print conservative media. On the other side is Donald Trump.

Yet a bet against Trump is looking about as smart today as paying for a degree from Trump University.

This was the first debate after Super Tuesday , in which Trump won seven of 11 contests and solidified his status as the front-runner. His advantage in delegates doesnt look that commanding at first blush, but the tally is misleading. The candidate in second place, Cruz, got a boatload of delegates from his home state of Texas. Hes got limited appeal elsewhere in the country. Rubio, meanwhile, has won just one contest -- and John Kasich, the fourth candidate remaining, hasnt won any.

In theory, any of Trumps competitors could overtake him. In practice, none of them are going to do it before the convention. At this point, pretty much everybody in politics realizes that the only way to stop Trump is to prevent him from getting a majority of delegates. That would create an open convention in Cleveland this summer, freeing delegates to support whomever they want -- and making it possible, in principle, for the party to nominate somebody else.

That is why conservatives have been issuing letters attacking Trumps qualifications to be president -- and, in some cases, declaring that they will not support Trump, even if their dissension increases the chances of Hillary Clinton becoming president. Its also why Romney, the partys 2012 nominee, gave a blistering speech on Thursday morning, attacking Trump as a fraud and a purveyor of hate.

And its why Trump spent most of the debate Thursday night fending off attacks. Rubio attacked Trump for starting a war of personal insults (true) and showing no interest in real policy (also true). Cruz questioned Trumps fidelity to conservative causes, arguing (correctly) that Trump has changed positions and signaled flexibility on his promises to get tough on immigration.

But the most persistent assault came from the Fox News moderators, who came prepared to hold Trump accountable for statements he has made. Chris Wallace pointed out that, according to independent experts, Trumps tax cut would create enormous new deficits. When Trump responded by claiming his plan for prescription drugs would save $300 billion a year in Medicare spending, Wallace put up a slide showing that Medicare puts only $78 billion into drugs in the first place -- and that you cant save more money than you spend .

Later it was Megyn Kellys turn. It was their first direct confrontation since last summer, when Trump claimed Kelly had asked hostile questions during another debate because she was menstruating. They began with some pleasantries, but afterward she put up some clips of her own -- pointing out three separate times that Trump had said one thing, and then later totally contradicted himself.

Trumps response was the same, as always. He insulted his questioners -- referring repeatedly to Little Marco, for example -- or changed the subject to his winning streak in the primaries and caucuses. In other instances, he simply made up more facts.

Trump actually looked rattled at a few points, which would be understandable given the sustained assault he received. And if you were scoring the debate on points -- that is, tracking whether Trump had responded to the arguments against him -- it wasnt even close. The other candidates and Fox hosts had him dead to rights. He never answered most of the claims.

But will it matter? At this point, it doesnt seem terribly likely. The one constant of this campaign has been Trumps ability not just to survive, but to thrive, despite incidents and issues that would have crushed other candidacies. He insulted a former GOP nominee who happens to be a war hero. His poll numbers held steady. He questioned the honesty of former President George W. Bush -- in South Carolina! His poll numbers held steady. He dithered on whether to disavow the David Duke and the Ku Klux Klan . And his poll numbers held steady.

Theres no single or simple explanation for why Trump has managed to defy the normal rules of politics. But clearly part of the story is his realization that a grasp of policy, consistency of viewpoint, and fealty to traditional conservative orthodoxy simply arent that important to many Republican voters. The base wants attitude, anger and strength -- and those are things that Trump can provide, more than anybody else on stage and maybe more than any politician in America.