Republican Party isn't sold on Marco Rubio

Republicans are supposedly even more worried that Donald Trump or Ben Carson could win their presidential nomination. Yet the one thing they could do about it -- send a clear signal in support of a single alternative -- still hasn't happened.

The obvious choice at this point would seem to be Marco Rubio, the only true coalition-style candidate remaining in the contest. He has been steadily gaining in the endorsements race ever since September.

But compared with other cycles, Republican party actors are well behind their pace: They're mostly sitting on their hands.

Why? It's hard to explain something that isn't happening, but here are several reasons they may be holding back:

1. Perhaps these Republicans are a lot less worried about Trump (and Carson) than they appear to be. If so, they may believe the nomination will be in relatively safe hands, and may be holding out in order to retain leverage over all the candidates.

2. It's possible the party actors are shying away from Rubio because of his previous support for comprehensive immigration reform. Some may oppose him on the issue; others may be concerned that a candidate with his history will find it hard to win over Republican voters.

3. Maybe there's something they know about Rubio that we don't know that's making them hesitate.

4. It's also possible Rubio isn't impressing people in person. The endorsements game isn't all about individual impressions, but a lot of these people -- not just politicians, but also campaign and governing professionals, donors and activists, formal party officials and staff, party-aligned interest group leaders and the partisan press -- spend time with the candidates, and their choices may be personal, regardless of what makes sense for the party. After all: If Rubio becomes president, they have to live (and work) with him.

5. Perhaps it isn't about Rubio at all. Maybe some high- profile Republicans just don't want to get involved. Parties normally care intensely about nomination politics. If they don't this year, something has gone seriously wrong with the Republican Party.

6. Or maybe the Republican party actors are moving in a certain direction, but they are just moving slowly. After a 12- day drought, Rubio picked up endorsements from House Republicans. He's still behind Jeb Bush in the race for major endorsements, but he's passed everyone else in the Republican field and is gaining. So maybe by New Year's Day, it will be obvious that Rubio is the party's choice, and it won't matter much that it took a few extra months.

Comment by clicking here.

Jonathan Bernstein, a politicial scientist and author, is a Bloomberg View columnist.