Night Strike wrote:Rasmussen polls "likely voters" because when you're polling political issues, those are the people who actually matter. 

 It doesn't make sense to poll a 100% random selection simply for the sake of selecting from a pool of all people, whether they are interested in political subjects or not.  Most other political polls will poll from registered voters and not all adults.

Ok, I can level on those two. In my post, I wasn't clear what I was referring to when I said what should be randomized: the population sample. 
Population in how I used it was semi-vague. It could have referred to the population of likely voters, people in the US, or even the people in Uzbeki-beki-beki-stan-stan-stan. I was referring to the population as being whichever target group (likely voters, in this case, sorry) and how they should be polled, not whether they're the right sample. Mybad.
The point about people who only use cell phones not being included in the poll is valid, but doesn't this apply to all other major polling groups?
That's what I was going to expand on when I got the chance. To an extent, yes. However, certain measures can be taken in a poll stratified for political alignment, race, class, etc. so that the effect is extremely low (Gallup does a lot of this, they actually hang up if they have too many people of a certain group, to make it more balanced). I looked around, and it didn't look like Rasmussen did this. It would pass for a high school or college freshmen level stats project, but not something I'd look to for accuracy.
 Even if you only poll landline individuals, you can still look into the data behind the poll numbers in order to analyze the political leanings of those who were polled.
Well, yeah, I wasn't saying that you couldn't do that! 

 I was saying if you did that or something that leaned towards landlines, you couldn't use it to extrapolate data onto others that aren't included in that group (which includes part of the likely voter in U.S. population). So, any conclusion from those numbers would have to state "In this poll blah blah, X +/- Y% of people with a landline...[rest]."
-rd