What's up with Rasmussen polling?

[CosmicDestiny]

Looking at the Iowa Senate polling, Rasmussen seems to have a much different vision of the race than other polls, even though it was taken before Braley's comments. 

Rasmussen's polls sometimes seem much more generous to Republicans, like in North Carolina, while in others, they seem friendlier to Dems (Generic Congressional ballot, Obama approval, and Wisconsin Governor). 

I assume this has something to do with Scott Rasmussen leaving, but why are its polls so contradictory?  It has Obama doing quite well approval rating-wise and shows the Dems with a 4 point generic ballot lead, yet it tends to give the bleakest picture to Senate Dems. 

Is there a good explanation for this?