A very interesting article in Real Clear Politics about September polling and what it means for the November Senate election. Their conclusion:
If this theory is right, we should expect to see these races continue on the basic trajectory we’ve seen over the past few weeks: Democrats holding at their current levels. Eventually, Republicans should begin or continue to improve, as undecided voters engage and make up their minds, and as Republicans narrow the spending battles. Even if this theory is true, it won’t occur in every race, but it will be the general tendency.
The entire article is filled with interesting data and worth a read.