Sen. Marco Rubio Sunday offered a detailed post-mortem of his own campaign, explaining the key junctures at which he failed to generate “the momentum front.” Chief among them: his mishandling of New Jersey Gov. Chris Christie’s attacks in the debate before the New Hampshire primary.

Rubio explained that he knew Christie was going to attack him, but he regarded Christie as a fading rival, and so he didn’t want to spend a significant amount of time in the debate sparring with a candidate whom he expected would have to drop out in a few days.