You are assuming that the primary states are all winner-take-all.
In 2008, most of them were -- and that's how McCain locked up the nomination without ever winning a majority in any state.
In 2012, however, many states have switched over to a proportional voting scheme -- e.g., win 25% of the vote, you get 25% of the delegates.
Under these circumstances it will be very difficult for anybody in this crowd to win a majority of the delegates before the convention.
True, I’m assuming that it’s winner take all, and not looking at the margins. However:
1, Cain is up in the national polls. Presumably that means that he would gain proportionally more delegates than Romney.
2, Cain is second everywhere that he is not first. Romney is third right now in NC and TX. TX, especially is a problem for Romney, because if it’s proportionally awarded, than he’s going to lose considerable ground to Cain.
Cain does worse under winner take all, so that’s the measure that I am using, because I figure that if it’s the trailing rather than the leading indicator, it’s a good sign that he has truly overtaken Romney.