Rasmussen is often cited by the rightwing because its numbers placate that fiction-loving sector of the voting public, but how does it arrive at its numbers? How do other polls arrive at theirs?
Scientific sampling has nothing to do with Rasmussen, which also "weights" its results by political party, but that ain't all--it uses robocalling to landlines only.
THIS article points out that there's also a significant difference in results between live interview polls and robocalls...as well as a significant difference between landlines-only polls and polls that include cellphones. It's an eye-opener.