Yes Jet some people nailed it. However you are missing the point entirely. The relevance of polls here is public perception. As long as reported results fall within a certain range covered by a significant body of polling, the public will tend to accept reported results.

In other words, had Romney won - by legit or by chicanery, it would be Rove being called spot on and not Silver. The spread of mainstream polls is basically a barometer of what the public will swallow, and any chicanery occurring that leads to a result that falls in that window + is not caught red handed will tend to pass undetected.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)