“It’s so brazen and obvious. … They recognize that Cunningham is a strong candidate, and they’re worried about holding on to that seat,” said Sen. Tim Kaine (D-Va.). “When Republicans are weighing in for somebody, they’ve made the judgment that they’re worried about Cal, and they’re not worried about her.”

Privately, Senate Democrats have been discussing the matter internally, with one fretting that Smith is “unelectable” in a general election and will be painted as a Bernie Sanders (I-Vt.) acolyte. Few in the party want to criticize Smith publicly since no matter who emerges as Democrats’ nominee, North Carolina is a must-win to take back the Senate.

But the GOP infusion of money is increasing worries about disarray.

“You want your strongest candidate. And if she’s not the strongest candidate, yes, it makes it much tougher,” said Sen. Jon Tester (D-Mont.), who supports Cunningham. “There’s just too much money in politics, and they spend it on trying to get the weakest candidate to run against” Tillis.

Democrats have used similar tactics in past Senate races in Missouri and West Virginia to elevate weak Republicans but decry the practice in their own internal politics. Sen. Debbie Stabenow (D-Mich.), who referred to Tillis as “extremely weak” in his reelection campaign, said the GOP is “known for voter suppression and playing games with voters, and they are taking it to new heights here.”

Still, some Democrats worry the effort will be at least partially successful.

“It's certainly made it more challenging to have over $2 million dumped into an ad buy against Cal Cunningham and what looks to be an attempt by Republicans to sway the primary,” said MaryBe McMillan, president of the North Carolina AFL-CIO, which endorsed Cunningham. “I still feel confident about his chances in the primary. It's just unfortunate that it's going to mean spending more resources.”

Faith and Power PAC's ads were placed by a media buyer used by a number of conservative organizations, and the PAC uses Chain Bridge Bank, which has deep ties to Republicans. Faith and Power PAC did not respond to emails. A spokesperson for the GOP super PAC Senate Leadership Fund, which also uses Chain Bridge Bank, did not respond to requests for comment.

Cunningham and his campaign have sought to amplify the super PAC's GOP ties.

“My gut tells me North Carolinians have a really strong BS meter. And this is triggering it," Cunningham said in a statement.

The turn in the race has been stunning: Just three months ago, Tillis faced a barrage of attacks from his own party and booked a massive TV buy to defend against a challenger accusing him of being insufficiently conservative. His challenger ultimately dropped out and Tillis scaled back his TV buy, though he is still working to win back his conservative base.