Two days after Senator Mary Landrieu (D-LA) debuted the first television ad of her 2014 re-election campaign, the Senate Majority PAC — one of the most well-funded and influential Democratic SuperPACs — released an ad of its own. While Landrieu’s ad made the case for her candidacy, Senate Majority PACs ad takes aim at her chief rival, U.S. Rep. Bill Cassidy (R-LA).

The ad, titled “Problem,” attacks Cassidy’s record in the House of Representatives, specifically criticizing him for having “voted to raise the retirement age to 70, to raise Medicare costs $6,000 a year, and…16 times to shut down the government.”

“That’s Congressman Cassidy’s record in the House. He’d hurt us even more in the Senate,” the narrator warns.

The ad is an obvious attempt to refocus attention on the deeply unpopular government shutdown—clearly more favorable terrain for Landrieu than the Affordable Care Act, which has been the most-discussed issue in the young campaign. Cassidy may recognize his vulnerability as a member of the unpopular House majority; he was one of just two Republican Senate candidates from the House to vote in favor of the Murray-Ryan budget compromise.

Senate Majority PAC will spend $250,000 to air the ad statewide. The SuperPAC has now waded into four 2014 Senate races; in addition to Louisiana, Senate Majority PAC has spent $111,940 opposing Arkansas Republican Tom Cotton, $339,906 opposing Senate Minority Leader Mitch McConnell (R-KY), and $1,061,056 supporting Senator Kay Hagan (D-NC.)

Early polling suggests that the race, which could end up deciding which party holds a majority in the Senate, begins as a virtual tossup.