How can we be sure changes in polls reflect real changes in opinion?

A technical response to a comment on last Friday's chart about Democrats' generic ballot polling

Dear readers,

I’m supposed to be taking the week/end off for Thanksgiving, but I couldn’t resist sending a short post here for paying subscribers. Let’s say the normal Chart of the Week and Sunday roundup are both off for the holiday, but members get a special treat to go with their morning coffee and leftover pie (don’t lie, we’re all doing it).

Before t…