The Koch brothers are moving their money to Wisconsin, where one of the groups affiliated with their super PAC Americans for Prosperity bought a $950,000 ad slot.

Democrat Russ Feingold has held consistent leads in the polls against Republican incumbent Sen. Ron Johnson, but as the margin diminished this past month, the billionaire brothers saw an opportunity, RealClearPolitics reported.

The ad will point out Feingold’s support of the 2010 health care law amid the news that premium prices are expected to increase next year. 

The TV buy signals a change in focus for the Koch brothers, as they announced in September that they were focusing on their field resources to support certain GOP senators. The Koch network had no plans to air any TV ads after Oct. 5.

[Kochs Shifting Resources to Threatened GOP Senators]

However, the Wisconsin ad buy appears to be the only TV spending for Americans for Prosperity in the final days before the election.

The overall network of political groups headed by the Koch brothers are on course to spend $250 million in this election. 

The Rothenberg & Gonzales Political Report/Roll Call rates the Wisconsin Senate race as Leans Democratic.