You could make a case from that statement, but if it takes three or four sentenses of explaining to get at what is being implied, it will not be a very effective attack. Besides, Obama parsed that statement before making it, so it would even be more difficult for the attack to stick.
I doubt we'll find irrefutable proof they're doing this, it's like the pretty girls in car commercials, the happy children in the laundry commercials, etc: subliminal.
That is why McCain's campaign mmade such a big deal out of this incredibly, even unbelievably, silly issue- to blunt a defining of her in the electorate's subconscious.