For the umpteenth time, Romney will not be the GOP nominee.
So by you logic, NO ONE can win the nomination. Since none of the republican candidates are polling 100%? Obama, never got above 50% of the dems voters in the primary. Did that mean he didn’t get most of them in the general? Sure he did.
Right now, the republican candidates are splitting votes. Happens when you have a large, diverse and strong group of candidates. Eventually someone will emerge and get the nomination. Then the party gets behind whoever that may be. And yes, there will always be plenty who say if my “candidate x” doesn’t get the nomination, I am sitting out the general. Sure some may do that, but most end up falling in line.
IN the end, it comes down to 6-7 states that will tip the presidency. And about 5-6% of those truly in the middle.