Tennessee is a Republican state and will likely stay one for a while, Gov. Bill Haslam said Thursday in reference to former Gov. Phil Bredesen, a Democrat, entering the U.S. Senate race for Sen. Bob Corker's seat.

But the governor said the GOP was equally confident 15 years ago.

"I think Tennessee is still a Republican state, but I think any Republican should always go into a race thinking 'I have to win a primary and I have to win a general,' and run the race accordingly," said the Knoxville Republican. "We've seen what's happened in other races."

Haslam, who spoke at the American Legislative Exchange Council summit in Nashville, said he agreed with U.S. Sen. Lamar Alexander, R-Tennessee, that Bredesen would be a formidable opponent, has name recognition and "comes with a lot of credibility."

The governor himself considered a Senate bid in September, but later said that he would not be running because he wanted to "remain completely focused" on his current job.

Bredesen officially launched his bid for U.S. Senate Thursday, announcing his run with an online video.

Bredesen — a political moderate and fiscal conservative who recently turned 74 — was the last Democrat to win a statewide election in Tennessee. He won all 95 counties in 2006 en route to his re-election as governor, after serving as mayor of Nashville in the 1990s.

But the political landscape has shifted to a Republican-controlled state since then.

Also seeking the Democratic nomination is James Mackler, an Iraq War veteran and Nashville attorney. Chattanooga Mayor Andy Berke has previously expressed interest in the entering the race but may be reticent to do so with Bredesen's candidacy.

On the Republican side, U.S. Rep. Marsha Blackburn, former U.S. Rep. Stephen Fincher and Dr. Rolando Toyos are seeking the GOP nomination.

Reporter Joel Ebert contributed to this report.

Reporter Jordan Buie can be reached at 615-726-5970 or at jbuie@tennessean.com. Follow him on Twitter @jordanbuie.