Barack Obama’s sudden decline in the polls have some of his supporters, and even some of John McCain’s backers, wondering whether the nosedive accurately reflects popular opinion.  Obama’s strength comes with younger voters, they note, and younger voters use cell phones more often as a substitute for land lines — and pollsters don’t call cell phones.  The implication is that Obama may be underrepresented by these polls and is performing stronger than people suspect.

Well, anything is possible, but as John Kerry can tell you, building hopes on massive youth turnout usually sets a candidate up for severe disappointment.  The supposed flood of new voters never arrived in 2004, when passions against the Iraq War ran much higher on college campuses than it does now.  Adding Joe Biden to the ticket certainly didn’t impress younger voters, either; 39% of the younger demographic said they’d be less likely to vote for Obama with Biden on the ticket, while 31% of them said they’d be more likely.  At the same time, in the same demographic, 50% said Palin was the right choice for McCain, while 36% said no.

If this concern had merit, we should have seen Obama overperforming against polling during the primaries against Hillary Clinton.  He had a solid grip on the youth vote throughout all of the polling, after all, while Hillary appealed to older voters.  Yet in state after state, Obama underperformed against polling predictions.  Only in North Carolina in the last three months did he overperform against polling expectations, and North Carolina was already a gimme for Obama.  Clearly the cell-phone issue didn’t underestimate Obama’s strength, as pollsters were busily overestimating it in state after state.

Polls have varying value as predictive models, but they’re better at reflecting trends.  No matter what anyone wants to think about cell-phone users and ObamaNation Gen-Xers, the trends all look bad for Obama this week, and the internals look especially weak.

Update: Who are cell-only voters?  More like us than people think — only a lot less likely to vote.