The conservative group Americans for Prosperity announced this week a $1 million advertising blitz against Democratic U.S. Rep. Gary Peters in Michigan for his support of the Affordable Care Act.

The advertising buy will span three weeks and cover television, radio and online ads aimed at holding Peters "accountable for his support of the Obamacare mess," the group said in a statement.

"Not only has Obamacare exploded on the launch pad, but it's causing Michiganders to have their plans cancelled and, in many cases, lose affordable access to the doctors they trust with their well-being," AFP's Michigan State Director, Scott Hagerstrom, said. "We're all forced to live with the Lie of the Year now, and Congressman Peters needs to be held accountable for repeating it."

Peters is battling former Republican Secretary of State Terri Lynn Land for the Michigan Senate seat being vacated by Sen. Carl Levin, who announced his planned retirement in March 2013.

AFP, backed by the conservative billionaire Koch brothers, also released an ad against North Carolina Democratic Sen. Kay Hagan highlighting her support of Obamacare ahead of the president's visit to the Tar Heel State on Wednesday.