Rep. Marsha Blackburn, the eight-term congresswoman from Tennessee, is expected to enter the race for Sen. Bob Corker's seat as early as Wednesday, a source familiar with the planning tells U.S. News.

Blackburn's impending Senate bid will serve as an early strike across the bow to the batch of Republicans eyeing the race following Corker's Tuesday announcement that he will not seek a third term.

Mark Green, a conservative state senator who was contemplating a Senate bid and consulted with Breitbart News chief Steve Bannon this week, instead will pursue Blackburn's House seat, according to the source.

Blackburn wouldn't be the first entrant into the race. Andy Ogles, who's headed the Tennessee chapter of Americans for Prosperity, entered the contest even before Corker announced he was retiring.

Other potential GOP candidates include Gov. Bill Haslam and former NFL star Peyton Manning, though after speaking with Manning, Corker indicated he would be surprised if the legendary quarterback mounted a campaign.

"I think it's possible," Corker said, according to NBC News. "I don't think it's going to happen."