The ad takes aim at state House Speaker Thom Tillis, the polling and money leader among the eight Republicans hoping to take on Hagan this fall.
"In the Senate, he'll support a plan that ends Medicare as we know it," says the voice-over in the ad.
David and Charles Koch are wealthy industrialists who help bankroll a number of groups, including Americans for Prosperity, which has spent around $7 million in North Carolina running ads that criticize Hagan for supporting the Affordable Care Act.
Senate Majority is expected to spend roughly $1 million airing the ad across North Carolina.
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