Dean Barnett thinks John McCain will leave the race on July 31, 2007. I would bet heavily against that, no matter how ugly the immigration debate gets. Unless a candidate actually runs out of money, why not wait until they actually start casting votes? Today polls still show McCain leading in Iowa, and so he could ride that momentum to New Hampshire, and then to March 5, and from there, who knows?
Also, I find it interesting that Romney supporters are already lashing out at Fred Thompson.