“In a way, Santorum had that opportunity in Michigan when Newt did not campaign there.”
Well, it depends on what the definition of “campaign” is, but Newt was on the ballot, and was on the news campaigning every day leding up to the primary, and he ended up getting 65,000 votes. Romney edged Santorum by just 32,000 votes, so it’s safe to assume that Santorum would have won the state had Newt dropped out prior to Michigan. I’m not saying that he should have dropped out then, or that he should drop out now, but it is certainly true that Newt staying in the race has been beneficial to Romney. It is also true that with both Newt and Santorum in the running, neither one will get 50%+1 in Alabama or Mississippi, which means that the states’ delegates will be allocated by proportional representation, thereby giving Romney several delegates from each state instead of 0.