- He's a former two-term governor and one-time mayor of Nashville
- Republicans face an open primary contest to replace Corker
In a statement on his website, he said he was running with the goal of improving how Washington handles spending and "fixing" the Affordable Care Act.
"We all know Washington is broken," he said in his statement
. "We need and deserve something better than we're getting from Washington. And we need and deserve a senator who can make that happen. I'm applying for the job."
Bredesen served as governor of Tennessee in 2003 through 2011. Before that, he served as mayor of Nashville from 1991 to 1999.
The 74-year-old hasn't run in a competitive race since his first gubernatorial election in 2002.
Republicans face an open primary contest to replace Corker, with Rep. Marsha Blackburn
and former Rep. Stephen Fincher both announcing bids to replace the two-term GOP lawmaker.
Democrats face a tough Senate map in 2018, defending 10 seats in states
that President Donald Trump won in 2016.
But Bredesen's entry in the Volunteer State gives the party another pick-up opportunity along with Arizona, where GOP Sen. Jeff Flake is retiring, and Nevada, where GOP Sen. Dean Heller is running for another term in a state Hillary Clinton won by a little more than 2 percentage points in the 2016 election.