NATE SILVER ON RASMUSSEN

Silver mentions in passing here that Rasmussen really isn't a very good polling company and gives his reasons here:

One definition of how "scientific" a poll is is the percentage of the adult population that it can potentially hope to reach. That isn't a complete definition, mind you -- it's more of a necessary than a sufficient condition -- but it isn't a useless one. By this definition, Rasmussen's polling isn't very scientific: because of certain shortcuts that they take, well over half of the American population will be physically unable to take one of their phone calls.

Rasmussen typically conducts its polling on weeknights, calling between 5 PM and 9 PM over the course of a single evening. They do not call phone numbers back, as most other pollsters do, in the event they don't get an answer the first time. They don't call cellphones -- only landlines. And they speak to the first person they get on the line if they speak to anybody at all; other polling firms use carefully-designed procedures to randomize the selection of respondent within the household (a typical mechanism is something like asking that the adult with the next birthday come to the phone).