The three-state parlay highlighted not just Santorum’s strengths, but Romney’s structural weaknesses. At the most elemental level, it remains true that Mitt Romney’s greatest challenge is winning votes. He has now lost elections to five different rivals over the course of his career. The last presumptive presidential nominee to have lost to so many opponents was Richard Nixon, and his losses were offset by a large number of electoral victories. Whatever Romney’s personal, moral, and intellectual merits, he has stood before voters more than two dozen times now. And they have nearly always expressed a preference for the other fellow—no matter who the other fellow is…

More worrisome, though, is what the results—particularly in Minnesota and Colorado—suggest about Romney’s infrastructure. When a campaign can’t keep track of a few thousand core supporters from one election cycle to the next, motivate them, and get them to the polls in a small caucus environment, there are only two explanations: Either the organization is incompetent, or the supporters have had second thoughts.

By the end of last week Romney was worried enough to do some of the contrast-drawing personally. “Senator Santorum and Speaker Gingrich, they are the very Republicans who acted like Democrats,” he said at an event in Atlanta. “And when Republicans act like Democrats, they lose.”

With a surfeit of political transparency and a shortage of self-awareness, the soundbite was a near-perfect distillation of the Romney candidacy.