If it's McCain vs. Obama what happens to illegal immigration?

Would McCain as president veto tough anti-immigration proposals since his record is pathetic on the issue? What would Obama do if he was handed the same proposals? Does this duo open the door to a third party candidate to run with a strong anti-immigration platform in their forefront? Personally i couldn't less if a 3rd party candidate took votes from McCain. I see him more bush-like than anything else