It's all about Hillary. The Pub candidates are almost just a generic Pub choice. Hillary gets about 45% no matter what, and gets a bit more of the undecideds with well known and more controversial Pub candidates (a bit surprising she gets the max 47% figure with Rubio however), but only a couple of points more at the moment. Once voters get to know the candidates better and some states vote in the primaries, the Pub numbers may become more variegated by candidate. That's my read anyway. It's really more of a poll about whether voters want a third term of Obama as POTUS.
Well she's below 45 against Carson too
