Jeb Bush’s super PAC is attacking Chris Christie and John Kasich. Kasich is running an ad against Bush. Christie and Bush have been criticizing Marco Rubio on his Senate absenteeism, among other things.

In terms of national polling, this makes little sense. Three of the four of them are in the single digits. Their combined RealClearPolitics polling average would just barely overtake Ben Carson for fourth place. Rubio is in third all by himself, but as Republican consultant Stuart Stevens notes, Bush could take a quarter of his vote and still lose.