If Hunter or Newt cannot pull off a dark horse upset, then it will be Romney by default. Rudy and McCain don't have a shot.
My vote goes in this order
1 Duncan Hunter
2 Mitt
3 Newt
4 McCain
5 Rudy
Rudy is a dead last resort if its against Hillary/Obama and me knowing Rudy cant directly effect abortion laws if he's in office just like Bush has no direct effect on making it against the law. I expect my lawmakers in Congress to make the laws preventing abortion so my litmus test goes there. I also believe Rudy would nominate a conservative to the court if put in the position. Hillary/Obama would put in a freak lefty.