I am having a lot of difficulty understanding how polls with no targetted partisan mix obtain such wide variances. The Dem majority (note I'm not saying over representation) in the partisan mix in July, transitioning to a GOP majority in the mix until now, and now the Dem majority again strikes me as not possible. This many people are not changing their party affiliation this rapidly.
Something has to be wrong, and not intentionally, with the sampling.
The issue of whether to hold partisan percentages constant, or allow them to flip, is an interesting. I tend to be an anti flipper type, but which is best, I really have no idea. Pity that the final polls, when the rubber meets the road, will tend to converge (folks coming home to their previous party affiliation?), so we will never really know the answer to this interesting question.