Did CBS milk their latest poll?

CBS rolled out a national poll yesterday, and here’s the headline number:

Obama 45, McCain 39 (July: Obama 45, McCain 39)

So Obama has a 6-point lead, and nothing seems to have changed since July. But when you dig into the details, there’s a strange partisan breakdown on page 15.* UNWEIGHTED WeightedTotal Respondents 1,034Registered Voters 906 851Total Republicans 317 (35%) 284 (33%)Total Democrats 381 (42%) 406 (48%)Total Independents 336 (37%) 344 (40%)*

In raw data, the partisan difference between Ds and Rs is 7%, but CBS pollster weighted the numbers and gave a 15% partisan difference. Interesting.