Political polls that include cell phone users show Obama leading McCain by an average of 10 points, versus just over five points in land-line-only surveys, notes a Sunday survey put together by Nate Silver, founder of the electoral projections site FiveThirtyEight.

The survey shows a snapshot of 15 polls conducted on behalf of media companies and by polling companies such as Gallup and Zogby. Six of those, including one released late Sunday by NBC and the Wall Street Journal, include cell phone users. The rest don’t.

The survey confirms a trend that the Pew Research Center noted late this September, although the differences between the surveys with and without cell phones was not statistically significant at that point.

Given the varying results of late regarding the size of Obama’s lead in the polls, there’s been a lot of discussion over the question of how accurate the polls are.

Much of the uncertainty over their "accuracy" centers around the question of who really is likely to show up to vote this year. Obama’s campaign is counting on young voter and African-American turnout while McCain’s campaign, according to this Washington Post article, expects the electorate to be similar in composition to the electorate of 2004.

You can hear more discussion between the experts on this subject from KQED’s Forum radio program, which aired Friday.

(Image: Fivethirtyeight.com )