Americans for Prosperity, the national conservative group backed by the billionaire brothers Charles and David Koch, is launching new ads attacking Democrats in Senate races in Louisiana, New Hampshire, Colorado and Michigan.

The ads hammer Democratic Sens. Mary LandrieuMary Loretta LandrieuSenate GOP rejects Trump’s call to go big on gun legislation Project Veritas at risk of losing fundraising license in New York, AG warns You want to recall John McCain? Good luck, it will be impossible MORE (La.) and Jeanne ShaheenCynthia (Jeanne) Jeanne ShaheenSenators pledge to pursue sanctions against Turkey over imprisoned American pastor Dems walk tightrope on Pompeo nomination Menendez rips characterization of Pompeo as 'nation's top diplomat' MORE (N.H.), as well as Michigan Senate candidate Rep. Gary Peters, for issues with ObamaCare. The ad running in Colorado has yet to be released but will hit Sen. Mark UdallMark Emery UdallSenate GOP rejects Trump’s call to go big on gun legislation Democratic primary could upend bid for Colorado seat Picking 2018 candidates pits McConnell vs. GOP groups MORE (D) on the law as well.

In Louisiana, the AFP’s ad features Christopher Schiff, a former Marine, recounting how ObamaCare caused his insurance costs to spike.

“Mary Landrieu said that ObamaCare is going to make things better. Better? Not for people like me,” he says in the ad. “I don’t think Mary Landrieu is looking out for my best interests or the people in Louisiana.”

The AFP’s ad in New Hampshire declares that it will be difficult to enjoy the “scenic drives” in the state while driving long distances to see the doctor, which the ad charges is likely under ObamaCare.

And in Michigan, a narrator declares that “Gary Peters said yes to ObamaCare — he’d do it to us again,” noting an estimated 225,000 Michigan residents that could lose their healthcare under the new law.

The AFP has been spending heavily on attack ads in competitive House and Senate races this cycle, investing more than $30 million since August alone to make the law a central focus in competitive races nationwide.

In response, national Democrats have launched an ongoing offensive against the Kochs, blasting them as anti-middle class and charging they’re trying to buy Senate seats to push their own agenda.

Democratic Senatorial Campaign Committee spokesman Justin Barasky said the Kochs are supporting Republicans in those states because they’ll know they “back their reckless economic agenda that enriches billionaires…while hurting the middle class.”

“Democrats will continue to hold GOP Senate candidates accountable for the policies and actions of the Koch brothers as these Republicans line up behind the Koch agenda that ends Social Security and Medicare as we know it, eliminates student loans, stops the renewal of unemployment benefits, fights against raising the minimum wage, and pushes our country to the brink of default in order to pay for bigger tax breaks for the wealthy and big corporations,” he said.

—This piece was updated at 1:20 to reflect comment from the DSCC.