Senate Majority PAC has put more money behind an attack ad against Louisiana Rep. Bill Cassidy, the top Republican running against vulnerable Democratic Sen. Mary L. Landrieu in one of this cycle’s most competitive races.

The super PAC, which boosts Democratic Senate candidates, purchased an additional $344,000 in air time for an ad against Cassidy, according to spending report filed with the Federal Election Commission.

The ad, first released in December, hits Cassidy for his votes to raise the retirement age, as well as his votes to shut down the government. The initial buy for the 30-second ad was $250,000, according to documents filed with the FEC. Senate Majority PAC Campaigns Director Ty Matsdorf confirmed the additional funds would go toward continuing to air the following spot:

https://youtu.be/UOucxyQWsnA

Cassidy, retired Air Force Col. Rob Maness and state Rep. Paul Hollis are running against Landrieu in November. Landrieu is one of the most vulnerable Democrats seeking re-election this cycle, and President Barack Obama lost the state by a 17-point margin in 2012.

Louisiana’s Senate race is rated a Tossup by Rothenberg Political Report/Roll Call.