Odd that he would increase Dem weighting. I wonder why. So, I guess what you are saying is that with more Dems sampled, the +16 among Independents moves the number less. Still, it would seem as if he has decreased Independent weighting, too. No? At the same time, it has seemed odd to me how Mitt can win Independents so regularly in other polls without them seeming to affect the result very much.
Rasmussen has been increasing Democratic weighting because Republicans aren’t answering the poll calls. According to the rules of polling science, he has to assume that his sample is still representative, and more people really are identifying themselves as Democrats.
(We have good reason to believe that Republicans simply aren’t answering the phone, thus skewing the people who do answer towards the Democratic, but it’s impossible to prove that.)
Let’s say that the breakdown is R33/D33/I33.
If 100% of Rs vote for Romney and 100% of Democrats vote for Obama, and if Independents went 50-50, then the result is 50%R-50%O.
Now let’s assume independents had a 16-point swing and all else were equal.
You’d have Romney = 0%D-100%R-58%I and Obama = 100%D-0%R-42%I. Calculate the total and it’s Romney=52.7% and Obama=47.3%. That’s “only” a 5.4% point swing.
Of course, the reality is that independents are not 33% of the voting electorate and Romney was already leading with them; I am simply positing a “best-case” scenario for independents to speak.