Democracy Corps (Stan Greenberg and James Carville's outfit) claims that polling results can be radically different when cell phone users -- usually left out of polls -- are included: Cell phones: why we think Obama will win the popular vote, too.
Voters reached on cell phones are not only more likely to vote for Obama, they are attitudinally and culturally distinct. They are less conservative but not perhaps more libertarian – giving both the NRA and gay marriage very favorable ratings.
Of course, we know those reached on cell phones are much younger and speaking to them on cell phones is obviously a precondition for getting their vote preference right. But cell phones are also critical to representing the new diversity of the American electorate. Those reached on cell are 29 percent minority...
Furthermore, response rates to polls have plummeted: the Pew Research Center says its response rate is down to 9%, compared with 36% in 1997. So polls represent a unusually responsive minority of land-line users, not the electorate in general.
This is not just important as we watch the electoral horse-race. So many spineless politicians watch the polls to determine what they should support or oppose, that if those polls are giving a distorted image of what the American people want it can have a real effect on policy.