The reason national polls are important is because it's kind of like the stock market. If you watch your portfolio, you'll notice that just about everything is either up or down in direct relation to whether the general indices are either up or down. How good or bad an individual stock is on a day-to-day basis is a lot of times just indicative of how it's behavior deviates from those general indices. And, they don't poll the states as often as they poll national for whatever reason they have.
But, I know. The green horn Obama is probably going to win. Despite the fact that the national polls tightened over the last few days. They haven't tightened enough.