I don’t know about you, but it seems to like Rasmussen has done amazing job at matching the trend present for President Obama’s approval rating. At the same time, with how much talk there has been from political pundits (on networks like CNN) about how the Democrats are headed for trouble in November, Rasmussen’s generic congressional ballot does not look that out of whack.
With that said, it is important to remember that you should pay attention to the trends represented from polls and not their absolute value because different pollsters’ methodologies will change the value of a poll. In the case of Rasmussen, it is highly likely that his strategy for determining "Likely Voters" tends to make his results more "conservative" than other pollsters; but this doesn’t (necessarily) mean that his polls are any less correct than the polls of other pollsters.
With that said, the real thing I wanted to point out on this thread was that, with the exception of a lower support from Black Americans (who still have an insanely high approval rating for Obama) the Tea Party movement’s demographics are pretty representative of America in general: