NASHVILLE (AP) — Former Tennessee Gov. Phil Bredesen has been calling potential donors to let them know he plans to join the race to succeed Republican Bob Corker in the U.S. Senate.

A prominent supporter confirmed he had spoken to Bredesen, the most recent Democrat to win a statewide race in Tennessee, about the decision Wednesday. He spoke to The Associated Press on the condition of anonymity because an official announcement wasn't expected until Thursday.

A Bredesen spokesman did not return several messages seeking comment.

Bredesen's calls to donors were first reported by the Nashville Post.

The Senate campaign of Republican U.S. Rep. Marsha Blackburn wasted little time in attacking Bredesen.

"Tennessee families want change and that is not what 74-year-old Democrat politician Phil Bredesen will bring to the United States Senate," said Andrea Bozek, a spokeswoman for Blackburn, 65. "Bredesen's views are out-of-touch with Tennessee values."

The other major Republican in the race is former U.S. Rep. Stephen Fincher. Nashville attorney James Mackler had previously announced a Democratic bid and vowed to contest Bredesen for the nomination.

Mackler called the race "a clear contrast between an Iraq War combat veteran that volunteers to serve his country against a career politician who only serves special interests."

Bredesen earned his fortune as a health care entrepreneur before serving two terms each as Nashville mayor and governor. He had largely withdrawn from politics and public life after leaving the governor's office in early 2011.

Democrats were heartened by the news that Bredesen planned to join the race.

"He'll make a great candidate; I couldn't be more pleased," said Will Cheek, a longtime Democratic activist. "Phil Bredesen is the kind of Democrat that can win in a state like this — he's done it before. I'm not sure he's not the front-runner at this point."

Nashville attorney Jeff Yarbro, one of just five Democrats in the 33-member state Senate, said voters are still familiar with Bredesen — and wiling to vote for him.

"People in Tennessee know Phil Bredesen, and the last time he ran, he won all 95 counties," Yarbro said. "His entry into the race confirms just how big an election year 2018 will be."

In expressing interest in running for the seat after Corker announced he wouldn't seek a third term, Bredesen acknowledged it would take a vast amount of money to wage a successful bid.

"Set against that, I love solving problems, and in Washington right now, there is plenty of material," he said at the time.

Bredesen narrowly won the 2002 governor's race to succeed unpopular Republican Gov. Don Sundquist, who spent much of his second term trying unsuccessfully to pass a state income tax to help bridge a widening budget gap from exploding costs of TennCare, the state's expanded Medicaid program.

Bredesen found a way to stem spiraling costs at TennCare by cutting 170,000 adults from the program and reducing benefits to thousands more. He won re-election the next year.

But those cuts became an issue later, when health care advocates made them a rallying cry against Bredesen while he was under consideration to become President Barack Obama's secretary of Health and Human Services in 2011. That job ended up going to Gov. Kathleen Sebelius of Kansas.

As mayor, The pro-business Bredesen lured the Houston Oilers to Nashville to become the Tennessee Titans and, as governor, persuaded Volkswagen to build its lone U.S. assembly plant in Chattanooga.