Polls can measure many things, but one thing they have a hard time getting at is intensity: Yes, people will tell a pollster whom they prefer in a campaign, but do they feel so strongly about their choice that they'll actually go out to vote?

Only elections can answer the intensity question, which is the most important factor in Tuesday's off-year governor's elections in New Jersey and Virginia and, increasingly, a special election in a New York congressional district. Intensity, as much as outcomes, may provide the best insight into national trends heading into the much more meaningful election in 2010.

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Joe Biden campaigns for Bill Owens in New York's 23rd District on Monday.

Last year, Barack Obama and his Democrats owned...