At least, that’s my guess.
…and that’s bad news for every candidate not named Jeb or Rubio, although possibly Ben Carson would find it congenial to have the focus be on the two Floridian candidates all night. And I’m being serious when I say that Jeb would probably profit from this fight: when you’re in fourth or fifth place, anything that blunts the momentum of the people currently in first and second place is likely to rebound to your benefit. Even if it’s just having a fight with the guy who’s more or less in third place.
Then again, Rubio also benefits from having the spotlight put on him, and for the same reason. So… watch the debate! It promises to be possibly quite the scrum.