For Walker and Bush, though, the evening was a disappointment. Both men planned their debate on the assumption that it was more important to survive than to win. Jeb Bush, after all, is the heavy favorite among the Republican Party’s big donors, a group that usually gets its way. Scott Walker has positioned himself as the single candidate least unacceptable to all major Republican factions—the kind of candidate who got picked in the era of the smoke-filled room and who still often prevails today (think Bob Dole for the Republicans in 1996, or John Kerry for the Democrats in 2004). Novelty candidates may flare from time to time, as they did in 2012, but Bush and Walker have the financial and political resources for the long march—or so they and their backers can believe.

That belief took a battering last night.

While Rubio had to be pushed toward the Todd Akin position on abortion, Walker willingly identified with it. That’s a dangerous position for the candidate whose selling point is that he’s uniquely acceptable both to ideological activists and to the electability-minded mainstream. The case for Walker is that he’s principled, if uncharismatic. The case against him is that he’s doctrinaire and unpersonable. Megyn Kelly’s question, “Are you too extreme?” gave Walker the opportunity to reveal a more nuanced, thoughtful, compassionate side. Such a self-revelation might have inspired party leaders to think, “Here’s our best back-up plan if Jeb Bush fizzles.” They now have to worry whether Walker might actually be a less-articulate and self-disciplined version of Ted Cruz.

As for Jeb Bush, he had the worst night of all. His job in these debates is to replicate Mitt Romney in 2012: to prove himself the most professional, most knowledgeable, and least-flawed choice in a big field. The activists may not like it, but as one after one of their preferred alternatives falters, they will have to submit to the reality, “Guys, there’s only one potential president on that stage.”

The essential precondition for replicating the Romney strategy is to avoid mistakes. Jeb Bush keeps stumbling into them. In May, Megyn Kelly hit Jeb Bush with the hardest—but also single most-predictable question—he faced as a candidate: Knowing what you know now, would you have supported the Iraq war in 2003? Bush famously floundered for nearly a week before at last pronouncing the answer: No. Last night, Kelly hit with the equally predictable follow-up: If Iraq was a mistake, as you now agree, what do you say to those who lost their lives in your brother’s war? Bush floundered again.

Bush’s troubles must raise two concerns in the minds of his supporters, one mildly disquieting, one extremely so.

Mildly disquieting: If a candidate can’t cope well with the predictable hard questions, how will he cope with the unpredictable hard questions?