While Rubio racked up a string of lawmaker endorsements this fall to rival Jeb Bush’s roster of congressional backers, his momentum on Capitol Hill has since stalled. His performance in the endorsement game, on the cusp of primary season, certainly isn’t fatal given Congress’ dismal ratings. But it does point to a struggle to be anointed the establishment candidate of choice.

The reticence around Rubio was punctuated by Sen. Lindsey Graham’s surprise move into Jeb Bush’s camp last week. The South Carolina senator, seen as one of the few congressional endorsements that could move the needle after he dropped out of the presidential race last month, went on to imply that Rubio is too green to be president…

“Rubio has a lot of support. Jeb has more,” Kinzinger said. “I’m 100 percent with Jeb. If at some point he decides he’s not running anymore — which I don’t foresee happening — but if he does, then we’ll take a look after that. But you know, Rubio may drop out too.”