Rep. Kevin Cramer’s, R-N.D., Senate campaign on Friday lashed out at an influential conservative group for wading into the midterm contest in North Dakota to praise Democratic Sen. Heidi Heitkamp.

Americans for Prosperity, a Koch brothers organization that has pledged millions to protect Republican majorities in Congress, is airing digital advertisements thanking Heitkamp for working with Republicans to pass a roll back of the Dodd-Frank financial reform law enacted by President Barack Obama.