NFL veteran Brett Favre is going all in for endangered Mississippi Sen. Thad Cochran, a Republican incumbent who is in the re-election fight of his life.

In a new television ad sponsored by the U.S. Chamber of Commerce, Favre, a native of Gulfport, Mississippi, urges voters to support Cochran who faces a challenging runoff next Tuesday against Tea Party insurgent Chris McDaniel, a state senator.

Mississippi Senate Race 2014: ABC News' '14 For 14'

"I've learned through football that strong leadership makes the difference between winning and losing. And when it comes to our state's future, trust me: Mississippi can win - and win big with Thad Cochran as our strong voice in Washington," Favre says in the 30-second ad. "Thad Cochran always delivers, just like he did during Katrina."

Favre calls Cochran a "proven and respected leader."

Get real-time election results and news about all the races you care about delivered right to your phone from now until November. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.