McCain is definitely the undisputed frontrunner at this point.
What will be interesting though is how many delegates he takes next Tuesday. A lot of the big states in play are not winner-take-all states, and there are plenty of states where Huckabee or Romney can expect to mount strong showings. McCain will likely win pluralities in a lot of the states, but I wouldn't be shocked to see this still be a race after Feb. 5 due to the way the delegates shake out. If after Tuesday Romney looks at the map and sees he might be able to take it to the convention maybe he keeps running, and Huckabee might keep going seeing that if it is still in play his delegates could give him a big say in the convention setup/platform/tenor of things.
Or McCain will romp and take everything. That could happen too. :)
It seems that one major point of disagreement is on how strongly to patrol the border. I don't think it's a good idea to give a bunch of Mexican-hating ranchers the ability to patrol the border and shoot anyone they think is an illegal alien.