Former congressman Denny Rehberg (R-Mont.), fresh off his 2012 loss to Sen. Jon Tester (D-Mont.), is considering giving it another go.

"I owe it to (my supporters), and to all the folks who I've served over the years, to keep listening and see how things develop," Rehberg told the Associated Press. "I'm not ruling anything out at this point."

Rehberg's four-point loss to Tester was widely regarded as a disappointment -- especially in a state that Mitt Romney carried by 13 points. It was also his second failed Senate campaign; he lost in 1996 to now-retiring Sen. Max Baucus (D-Mont.) in a close race.

Other potential GOP candidates include freshman Rep. Steve Daines and state Attorney General Tim Fox. Former state senator Corey Stapleton and state Rep. Champ Edmunds are already in the race.

The biggest question for now is whether popular former governor Brian Schweitzer runs on the Democratic side. If he does, it might dissuade big-name Republicans from running.