MINNEAPOLIS (WCCO) — The results of this week’s primary would have been a shock if you solely looked at the polls.

For instance, the latest NBC News/Marist poll showed Tim Pawlenty with a commanding 19-point lead over Jeff Johnson. It also projected Lori Swanson would have a tighter margin with Tim Walz.

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Hamline Professor David Schultz has written extensively about polling.

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He says one reason why Minnesota polls can be off is that we are one of the few states that have same-day voter registration and those voters are not picked up by pollsters.

“It does throw things off because about 15 percent of Minnesotans register to vote on the day of the election,” he explained.

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Schultz says another reason why political polls are increasingly off is that they don’t have a high enough percentage of cell phone users and rely too heavily on land-lines.