The congresswoman is locked in a tight race with Democratic former Gov. Phil Bredesen.

Rep. Marsha Blackburn (R-TN). Getty Images

President Donald Trump travels to Tennessee on Tuesday to aid Republican efforts to win a tight Senate race critical to the fight to control the chamber in November's midterm elections. The president will hold a fundraiser and campaign-style rally in Nashville to boost GOP Rep. Marsha Blackburn and attempt to knock down Democratic former Gov. Phil Bredesen. They are vying for the Senate seat currently held by Republican Sen. Bob Corker, who declined to run for a third term. Making things more complicated, Corker hasn't given a full-throated endorsement to Blackburn, and he has said he considers himself a friend of Bredesen's. Polls have shown a close contest between Blackburn, a longtime member of Congress who has run as a staunch Trump supporter, and Bredesen, a two-term governor who last won a statewide election in 2006. Bredesen hopes to win a seat in a state that last had a Democratic senator in the mid-1990s.

The Tennessee race holds major stakes for Republicans' push to keep or expand their 51 to 49 seat majority in the Senate. Winning Corker's seat could help Democrats cancel out other possible losses in 2018 Senate elections, as the party tries to defend 10 seats in states Trump won in 2016. Trump has already gotten himself involved in several of those races. He has made trips in part to damage Democratic senators such as Joe Donnelly of Indiana and Joe Manchin of West Virginia. He has repeatedly slammed red-state Senate Democrats for not supporting his agenda.

Blackburn hitches her wagon to Trump

Corker hesitates to take a side

Corker has notably hesitated to take sides in the Senate race, prompting questions about whether he could lead other Republicans to shy away from Blackburn. Last month, the senator said he would not campaign against Bredesen, whom he called a "friend." Corker said he had a stronger working relationship with Bredesen than with Blackburn. The senator was the mayor of Chattanooga when Bredesen was governor. Still, Corker said he is "supportive" of Blackburn and donated to her campaign. Bredesen, like some other Democrats running in key red state elections, has avoided criticizing Trump. "I don't want to come across as somebody who is the toy of the national Democratic Party," Bredesen told CNN in late April.

Phil Bredesen, former governor of Tennessee. T.J. Kirkpatrick | Bloomberg | Getty Images