here are my odds right now:
Trump: 45%
Cruz: 30%
Rubio: 15%
Christie: 10%
It's really starting to look like Christie might have a better shot of emerging as the establishment choice than Rubio does.
I wouldn't dismiss Carson too quickly, but if after being demoted to an undercard candidate he manages to surpass Kasich, Bush and Rubio, he would be the comeback kid.
Even if October, when Carson was doing better, I still thought his chances were fairly low. Even if he wins Iowa, he's not going to win the nomination. Republicans like him and he has a devoted group of supporters, but it's clear that most don't see him a president.