GENERATION CELL….Are telephone surveys that don’t include cell phones accurate? Apparently so, even as the number of cell phone users continues to grow. Here’s the latest from Pew, which just conducted a survey of both cell and landline users:

Cell-only respondents are significantly more likely than either the landline respondents or the cell-mostly respondents to support Barack Obama and Democratic candidates for Congress this fall. They also are substantially less likely to be registered to vote and — among registered voters — somewhat less likely to say they are absolutely certain they will vote.

Here’s what this boils down to. In the landline-only sample, Obama was ahead by five points, 46-41, but in the combined sample he was ahead by eight points, 48-40. Among people who are certain of their vote, Obama leads by eight points in the landline sample and ten points in the combined sample.

This suggests that although we’re starting to get to the point where pollsters risk some genuine distortion if they don’t include cell users in their surveys, we’re not there yet. The differences in the Pew poll are still small and might just be a sampling fluke. Within a few years, though, this is likely to change, and in the meantime maybe it would be worth someone’s time to do a mega-survey (say, 10,000 respondents) to get a better handle on this.

UPDATE: One more thing, though: it’s worth noting that among cell-phone-only users (i.e., people who don’t have landlines at all and use cell phones exclusively), Obama beat McCain by a whopping 29 points, 61-32. The reason it didn’t affect the overall numbers much is because — so far — they’re still a pretty small proportion of the population. Also, there’s this interesting demographic breakdown of cell-only and cell-mostly users:

Compared with all respondents reached on a landline, both groups are significantly younger, more likely to be male, and less likely to be white. But the cell-only and cell-mostly also are different from one another on many characteristics. Compared with the cell-only, the cell-mostly group is more affluent, better educated, and more likely to be married, to have children, and to own a home.