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WASHINGTON — Sen. Bob Corker has decided against running for re-election.

The Tennessee Republican had been reconsidering his earlier decision to retire, but his chief of staff, Todd Womack, said Tuesday that "the senator believes he made the right decision in September and will be leaving the Senate when his term expires at the end of 2018."

Corker, who has clashed with President Donald Trump, would have faced a potentially brutal primary against Republican Rep. Marsha Blackburn, a conservative favorite, for the right to face former Tennessee Gov. Phil Bredesen in November.

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His decision helps the party avert another battle in an ongoing war between its establishment and anti-establishment wings. Though Blackburn has served in the House since 2003, she is popular with Tea Party activists.

In a statement Tuesday, Blackburn thanked Corker for his "dedicated service" to the state.

Democrats believe that the recruitment of Bredesen, who won gubernatorial races in 2002 and 2006, gives them a chance to score an upset in a state that hasn't elected a Democrat to the Senate since Al Gore in 1990.

Womack insisted that Corker had a shot at winning the primary and the general.

"Based on the outpouring of support, we spent the last few days doing our due diligence and a clear path for re-election was laid out," he said.

But Corker's approval rating in the state had dipped after he sharply criticized Trump last year, and Corker became a target of national conservative groups aligned with the president.

Specifically, Corker openly questioned Trump's competence and stability, leading to a long back-and-forth with the president over traditional and social media. Shortly after that, Corker announced he would not seek re-election, a move he recently began reconsidering.

On Tuesday, through his top aide, he put the idea of re-entering the fray to rest.