Outside money is pouring into North Carolina's races.

Andy Taylor, a political science professor at N.C. State University, offers several reasons why third-party groups are spending millions attacking Republican gubernatorial nominee Pat McCrory and U.S. Sen. Elizabeth Dole.

* Close races: Polls in both the Senate and gubernatorial races are closer than expected, giving national groups hope that they can influence the outcome with a well-timed ad.

* Stand by your ad: A 2002 campaign law requires candidates to personally approve their ads, but outside groups can run harsh attacks without a backlash.

* Contribution limits: State and federal laws limit the amount donors can give directly to candidates, so some give to third-party groups to further their efforts.

Taylor says the increasing influence of third-party ads means candidates have less control over their message, but they gain "plausible deniability" on attacks.

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