Just to inject the proper note of caution to all those excited Republicans outs there. Rasmussen had the best results of the pollsters in 2002, 2004, and 2006. But they were only average in 2008, and in 2010, below average. In all those years, Rasmussen tended, though this was not true of every poll, to overestimate Republican strength. The numbers that have conservatives so giddy might be a few points high.
As in all elections, however - and this seldom comes up in all the criticism of which polls are better than others - turnout is hard to predict. The polling experts like to talk about cell phones and windows and sampling - because they all have to lower their voices when it comes to turnout.