A liberal PAC is the latest outside group to weigh into North Carolina's U.S. Senate race.
The Patriot Majority USA PAC is spending $500,000 on an ad that accuses Senate candidate Thom Tillis, the state House speaker, of siding with health insurance companies and special interest groups.
The PAC is the second outside group to air ads against Tillis in the race. On the other side, Americans for Prosperity, supported by the conservative Koch brothers, has spent more than $6.5 million on ads attacking Democratic incumbent Sen. Kay Hagan.
Hagan has criticized the Koch brothers and unidentified special interests for running such ads. Patriot Majority, like AFP, doesn't disclose its donors.
Tillis spokesman Jordan Shaw called out Hagan.
"While Kay Hagan denounces the use of outside funds against her, liberals in DC are spending hundreds of thousands of dollars falsely attacking Thom Tillis," he said. "Where is Kay Hagan's statement condemning these ads? Liberals in DC know that Thom Tillis is the candidate to beat Hagan."
Hagan spokeswoman Sadie Weiner said Hagan has criticized not only the AFP ads but what she calls the Koch brothers' conservative agenda. Hagan supports the Democratic-sponsored DISCLOSE act that would require more transparency from political groups.
"Kay was named the most moderate Senator (by the National Journal) because she always puts North Carolina first unlike Thom Tillis who has pushed an outside, special interest agenda that cut education spending and lowered taxes for the wealthy," Weiner said.
Weiner said has "no control over outside groups."
The Patriot ad is the latest to attack Tillis, who faces a handful of other Republicans in the May 6 primary. Tillis has out-raised his rivals with the support of GOP leaders in Washington.