The bombshell Sept. 26 announcement by U.S. Sen. Bob Corker, R-Tennessee, that he won't run for re-election next year immediately turned attention to his potential replacement.

His decision to not seek a third term had the potential to shake up Tennessee's 2018 gubernatorial election and congressional races.

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Here's a list of who is in and who is out of the race to replace the two-term senator (in alphabetical order):

In the race

U.S. Rep. Marsha Blackburn

Party: Republican

Website: https://www.marshablackburn.com/

The longtime conservative Brentwood lawmaker launched her campaign Oct. 5, one hour after Gov. Bill Haslam said he would not enter the race.

Her entrance into the race catapulted her into immediate frontrunner status and was further bolstered after Twitter pulled her campaign ad — a decision which was later reversed.

A frequent backer of President Donald Trump, Blackburn labels herself as an unabashed hardcore conservative who is proud of being politically incorrect.

Former Gov. Phil Bredesen

Party: Democrat

Website: http://www.bredesen.com/

The former Nashville mayor was the last Democrat to win a statewide race in Tennessee and has been previously mentioned among Democrats but said he had no interest in re-entering public office. Although he initially said he was not interested in running for the seat, Bredesen reconsidered and was courted by state and national Democrats.

He launched his campaign Dec. 7, setting off what many expect will be a blockbuster race.

Former U.S. Rep. Stephen Fincher

Party: Republican

Website: https://www.stephenfincher.com/

When the farmer from Frog Jump opted to leave Congress in 2016, he maintained a sizable war chest he could use in a run for the seat. Since's Corker's announcement Fincher launched a statewide listening tour and formally announced his run on Oct. 22.

Touting his credentials as a "results-oriented" conservative, Fincher could appeal to establishment Republicans.

James Mackler

Party: Democrat

Website: https://www.jamesmackler.com/

The Nashville attorney and Iraq war veteran launched his campaign on April 16.

Despite initially netting thousands of dollars in donations to bolster his campaign, with his relatively low name recognition and Bredesen in the race, Mackler faces an uphill battle for the nomination.

Rolando Toyos

Party: Republican

Website: https://toyosforsenate.com/

The founder and CEO of a business with clinics in Memphis and Nashville, Toyos previously served as the official ophthalmologist to the Memphis Grizzlies for about 10 years. He announced his campaign on Oct. 25.

Dropped out

Andy Ogles

Party: Republican

The former Americans for Prosperity-Tennessee head launched his bid for Republican nomination for the U.S. Senate seat on Sept. 14. He dropped out of the race on Nov. 15.

Not running

Republicans

Joe Carr

The frequent Republican candidate, who challenged U.S. Sen. Lamar Alexander and Black in recent elections, had tossed around the idea of running for the seat before Corker's decision. The day Blackburn announced her candidate Carr said she would be supporting her. He has since opted to run for the state Senate.

State Sen. Mark Green

The Clarksville Republican had flirted with the idea of running for the seat — and had been seen as a possible challenger against Corker. Green met with former White House aide and Trump campaign strategist Steve Bannon at a campaign rally for Alabama U.S. Senate candidate Roy Moore. Green launched a campaign for Blackburn's congressional seat after she enter U.S. Senate race.

Gov. Bill Haslam

Party: Republican

Earlier this year the Knoxville Republican didn't rule out a potential run for U.S. Senate. After Corker's announcement, Haslam was encouraged by many, including U.S. Sen. Lamar Alexander, to considering running for the seat but ultimately opted against it.

Lt. Gov. Randy McNally

The longtime state senator said Tuesday he did not plan on running for the seat.

Former Lt. Gov. Ron Ramsey

"I'm through running for office," he said after the announcement. "There is life after politics."

Dr. Manny Sethi

An orthopedic trauma surgeon at Vanderbilt University Medical Center, Sethi founded Healthy Tennessee, a nonprofit that holds health fairs and clinics around the state that focuses on prevention and how to be healthier. Sethi has traveled to Washington, D.C., twice in the last year to testify before the U.S. Senate and speak on a White House panel on reforming the Affordable Care Act. He addressed rally-goers when President Donald Trump visited Nashville.

On Oct. 11, Sethi said, "After much careful consideration I have decided to not seek the U.S. Senate seat left open by Senator Corker's vacancy."

Sethi said the decision does not preclude him from considering a statewide run in the future.

2018 gubernatorial candidates

Spokespersons for U.S. Rep. Diane Black, House Speaker Beth Harwell, Knoxville businessman Randy Boyd, Franklin businessman Bill Lee and former state Sen. Mae Beavers each said they had no interest in seeking the seat.

Other congressional Republicans

U.S. Rep. Chuck Fleischmann said he had not thought about his future. U.S. Rep. David Kustoff did not respond to a request for comment about the interest in the Senate seat.

Democrats

Nashville Mayor Megan Barry

Mayor Megan Barry is popular in Nashville and a star among Tennessee Democrats, but she says she's focused on being mayor.

"While I appreciate those who have asked me to run for this open seat, my focus is on improving the quality of life for Nashvillians by building a better transit system, expanding our supply of affordable housing, improving educational outcomes for students, and keeping families safe," Barry said. "I believe I can best accomplish these goals as mayor."

Chattanooga Mayor Andy Berke

Berke, a former state senator in his second term as mayor of Chattanooga, frequently gets mentioned as a potential statewide candidate for Democrats. He has been in talks with family and people around the state about launching a potential bid. After Bredesen launched his bid, Berke said he would support the former governor.

State Rep. John Ray Clemmons

The Nashville lawmaker was once traveling the state before making a decision about a potential run.

U.S. Rep. Jim Cooper

The longtime Nashville congressman ran for U.S. Senate in 1994 unsuccessfully.

"Jim is not running for Senate," the congressman's spokesman Chris Carroll said. "He is honored to serve Middle Tennessee in the U.S. House, and he is running for re-election."

Karl Dean

The former Nashville mayor is currently running for governor and says he's not interested in pivoting to the Senate race.

"Mayor Dean's interest is in the state of Tennessee and serving as governor," a campaign spokesperson said.

Bill Freeman

The Nashville real estate mogul, top Democratic donor and 2015 Nashville mayoral candidate had been considering a run for governor but declined to enter the race earlier this year.

Although he has nixed a potential run for the seat, Freeman encouraged Bredesen to enter the race.

State Sen. Jeff Yarbro

Despite the Nashville-based lawmaker initially saying he was considering running for the seat, he has since said he wanted to focus on Tennessee rather than Washington, D.C.

Dave Boucher, Jordan Buie and Holly Fletcher contributed to this report.