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