How Is It Different Polls Produce Different Results?

With midterm elections just about three weeks away, political polls are more important than ever. Mark Blumenthal, senior polling editor at the Huffington Post and co-founder of pollster.com, tells Linda Wertheimer the different results are attributed to how a "likely voter" is defined. Pollsters can either take a narrow look at likely voters, or they look at all registered voters.

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