I think he does this to compensate somewhat for the lack of cellphone #'s in their sample. I heard Scott say the other day that, their data suggests that actually polling a representative sample of cell phones would move the numbers " a couple of percent" toward the Democrats".
Maybe, this is one of the ways they are trying to correct for that?
Where did this myth start, that only punkie Democrats use cell phones and Republicans are just old fuddy-duddys who only use land lines?
That’s another plausible explanation but I would like to see a large sample of “land lines” vs “cell phones”, to see whether it really is such a large difference in party identification.