Former Rep. Denny Rehberg (R-Mont.) is considering another Senate run following Sen. Max BaucusMax Sieben BaucusSteady American leadership is key to success with China and Korea Orrin Hatch, ‘a tough old bird,’ got a lot done in the Senate Canada crossing fine line between fair and unfair trade MORE's (D-Mont.) retirement announcement.

"Ever since Max announced his retirement two days ago, my phone has been ringing off the hook. The encouragement I've been getting from Montanans to take a serious look at this race has been overwhelming," Rehberg told The Associated Press in a Thursday email. 

"I owe it to them, and to all the folks who I've served over the years, to keep listening and see how things develop. I'm not ruling anything out at this point."

The comments are something of a reversal for the former congressman, who lost a race to Sen. Jon TesterJonathan (Jon) TesterEMILY’s List president: Franken did 'right thing for Minnesota' Reforming veterans health care for all generations of veterans Trump and Republicans deliver gift that keeps on giving for Americans MORE (D-Mont.) last fall. 

He said in January he would definitely not run for office again, and has since taken a job at a Washington-based firm.

Baucus's retirement creates a big opportunity for the GOP to pick up a seat in the GOP-leaning state. 

Former Gov. Brian Schweitzer (D) is likely the Democrats' best hope to run for the seat, and told The Hill earlier this week that he'll weigh a bid. 

Rep. Steve Daines (R-Mont.), who replaced Rehberg in the House, is also considering a bid, while former state Rep. Corey Stapleton (R) and state Sen. Champ Edmunds (R) are already in the race.

Some Republicans in the state have mentioned former Montana Gov. Marc Racicot (R) as a possible candidate, while Democrats say if Schweitzer doesn't run, EMILY's List President Stephanie Schriock (D) and state Secretary of Public Instruction Denise Juneau (D) are possible options.