Kerry needs to move things nationally by 6-7% to get Missouri.
If he can't move it 7, he wastes money in Missouri.
If he does move it 7, he doesn't need Missouri.
The right call for Kerry
Right now, he needs to protect the vulnerable Gore turf (WI, IA, NM especially), and start dumping resources (relative to the number of respective EVs) into the only Bush states he has any reasonable shot of winning at this point - FL, WV, and NH.
OH even, at this point, is out of reach. If I were running the Kerry campaign, I would be pursuing a "Florida or bust" strategy.