Over the years, polls have gotten very accurate in predicting who will win elections. But obviously, pollsters were wrong - very wrong - in predicting result of the New Hampshire primaries.

Nine individual polls (even Hillary's own poll) showed that Obama had a significant lead - some even had him with double-digits leads. So how did the pollsters got it so wrong?

There will be a serious, critical look at the final pre-election polls in the Democratic presidential primary in New Hampshire; that is essential. It is simply unprecedented for so many polls to have been so wrong. We need to know why.

But we need to know it through careful, empirically based analysis. There will be a lot of claims about what happened - about respondents who reputedly lied, about alleged difficulties polling in biracial contests. That may be so. It also may be a smokescreen - a convenient foil for pollsters who'd rather fault their respondents than own up to other possibilities - such as their own failings in sampling and likely voter modeling.

Gary Langer, the director of polling at ABC News, explains: Link [ABC World News Webcast, Flash video] | The Numbers, Gary's blog - Thanks Zach!