If you had judged the state of the Republican primary one month ago by surveying the elite punditry of the moment, you would’ve come away with the sense that Marco Rubio was a runaway favorite to win the GOP presidential nomination.

This assessment stood in stark contrast to both national and early state polls, none of which showed (or today show) Rubio anywhere close to the lead, and only one of which (New Hampshire) had him holding a tenuous grasp on distant second.

The logic underlying the pro-Rubio analysis, rooted in the perfectly sensible assumption that Rubio’s support will climb as the Republican field winnows, isn’t entirely unfounded. The field of candidates who could plausibly gain significant numbers of endorsements within the party is much more fractured than the field of “insurgent” candidates. If and when the former field shrinks, the thinking goes, Rubio stands to consolidate enough support to find himself in league with Donald Trump and Ted Cruz.

Unless, of course, he doesn’t.

When other candidates have faltered, Trump and Cruz have surged, but Rubio has barely benefited at all. Nationally he enjoys less than 11 percent support, and falling. In Iowa he’s holding steady at 12.5 percent. He’s enjoying a modest climb in New Hampshire along with other candidates, and in South Carolina both he and Cruz are experiencing small surges, but Cruz at a significantly faster clip.