"Skipping Cell Phones Skews Polls to GOP"

I think that I already assumed that this was the case, but it is useful to have in confirmed. Still a five percentage point adjustment factor is a useful rough number to have (it will obviously vary some race to race).

Republicans received a boost over Democrats in landline-only telephone polls, according to a new study by the nonpartisan Pew Research Center.

Polls this fall that reached only landline phone numbers ended up giving Republicans an extra five percentage points compared with polls that dialed both landline and mobile phones, the study concluded. Pew said that’s because almost a quarter of U.S. homes don’t have a landline telephone number, and cell phone users tend to be younger and more Democratic. . . .

For instance, Pew’s final generic ballot survey of the fall had Republicans up 51% to 39% among voters reached by landline, double the 48% to 42% lead in a sample that included cell phone respondents.