The Democratic group Senate Majority PAC is going on the air in two hotly contested Senate races in Arkansas and Michigan with ads tying Rep. Tom CottonThomas (Tom) Bryant CottonSunday Shows Preview: Emmanuel Macron talks ahead of state dinner Rand Paul under pressure as Pompeo hunts for votes GOP senators raise concerns about babies on Senate floor MORE (R-Ark.) and former Michigan Secretary of State Terri Lynn Land (R) to the billionaire Koch brothers and blasting them on their healthcare positions.

The ads are part of a multi-state, multi-state push to counter the millions of dollars of attack ads run by Americans for Prosperity, a group backed by Charles and David Koch. Senate Majority PAC is spending $500,000 on the two ad buys.

"You already know that billionaires are paying for Terri Lynn Land's Senate race. What they already know is that with Land insurance companies will be able to deny you coverage when you get sick, women's access to preventive healthcare will be cut while their costs will increase. Now you know what the billionaires know: They know Terri Lynn Land answers to them, and not us," says the ad attacking Land in Michigan.

"Corporate special interests are spending millions to smear Mark PryorMark Lunsford PryorMedicaid rollback looms for GOP senators in 2020 Cotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm MORE and elect Tom Cotton. Why? Before Congress, Cotton got paid handsomely working for insurance companies and corporate interests. Now, Cotton wants to end Medicare's guarantee, giving billions in profits to insurance companies while costing seniors $6,000 more a year. The real Tom Cotton? A politician we just can't trust," says the ad attacking Cotton and backing Sen. Mark Pryor (D-Ark).