Senate Majority PAC brackets Tillis

As expected, Senate Majority PAC began running an ad in support of U.S. Sen. Kay Hagan's re-election bid this week, slamming one of her main Republican rivals as too closely tied to the Koch brothers. 

This is the second foray this election cycle into North Carolina for Senate Majority, a independent spending group that backs Democrats running for U.S. Senate. 

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.

That claim is very similar to one made by Patriot Majority in an ad broadcast earlier this year. Tillis has not said exactly what he might support in terms of health policy when he reaches the Senate. 

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.