If Walker wins re-election he's running it doesn't matter how much he wins by every move he's making at this point is one for primary voters in '16. He has a very clear path to the nomination unlike Jeb, Christie, Cruz, & Paul he could sweep the Midwest states & elsewhere and lock up the nomination. I see him as the only candidate right now who could unite both factions because Jeb, Christie, Kasich, Cruz or Paul can't do that.
To be fair, Pence could probably do that as well. Besides Kasich, he's the other dark horse that could make a run, and I think it one of them will, but its a coin flip as to which one.
I could swear that I've seen before that the establishment is wary of Walker.