Gallup, Rasmussen and Reuters/Ipsos are all doing national tracking polls. Here are the results of this month up through yesterday, Sept. 17. All to polls agree that things turned in Obama's favor as of Sept. 5, the day of Bill Clinton's speech, but Rasmussen and Gallup think it was a bounce, while Reuters/Ipsos thinks it's a trend.
I still think tracking polls are a lot of math and hard work for not much purpose, not unlike a very accurate horoscope. The main use is to calibrate polling companies against others, and here we can see Rasmussen is almost always the most right leaning of the companies, sometimes to a very noticeable amount. If we take the median of the three, we see a bounce instead of a trend. Looking at the individual swing state polls gives us a very different view, and to my mind a more accurate one.