UPDATE: Politico reports that Sen. Bob Corker has decided against a bid for re-election and will continue onward with his planned retirement.

Todd Womack, Corker's chief of staff said:

“Over the past several months, Senator Corker has been encouraged by people across Tennessee and in the Senate to reconsider his decision not to seek re-election. 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. However, at the end of the day, 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. When he ran for the Senate in 2006, he told Tennesseans that he couldn’t imagine serving for more than two terms because he has always been drawn to the citizen legislator model and believes public service should be missional. This has been the greatest privilege of his life and he is forever grateful to the people of the Volunteer State for the opportunity to serve our state and country.”

Corker's fellow United States Senator Lamar Alexander weighed in as well, saying:

“Bob Corker is a terrific United States senator and a good friend. I was disappointed in his decision not to run for reelection but respect that decision. I invited Marsha Blackburn to breakfast this morning. We had a good discussion about a variety of issues that we both care about and how we might work together to make the Senate a more effective institution.”

PREVIOUS STORY: Outgoing Sen. Bob Corker is reconsidering his retirement as Republicans in Tennessee worry about potentially losing his seat, Politico and The Washington Post reported.

Some members of the GOP in Corker's home state want him to run again in this year's midterm elections, according to Politico. The Tennessee Republican, a frequent critic of President Donald Trump, said in September that he would retire after his current term ends.

Despite their clashes after Corker publicly worried about Trump's competence, the president reportedly wanted him to run for Senate again.

In Corker's absence, the race will likely pit Rep. Marsha Blackburn, R-Tenn., against former Democratic Gov. Phil Bredesen. While the state has proven reliably Republican in recent elections, Democrats see opportunity in places where they were not previously competitive after Sen. Doug Jones won the Alabama special election last year. The current minority party is trying to win control of the chamber despite a daunting re-election map.

One recent Tennessee poll that oversampled Republicans even showed Bredesen with a two-point advantage, Politico reported. Widely followed sites that rate congressional elections show mixed signals for the GOP: the Cook Political report rates the race as a toss-up, while Sabato's Crystal ball rates it as "likely" Republican.

Representatives for Corker and Blackburn's campaign did not immediately comment to CNBC.

Blackburn's campaign told the Post that sexism led to concerns about the congresswoman's ability to win the election.

"We aren't worried about these ego-driven, tired old men. Marsha has spent her whole life-fighting people who told her she wasn't good enough and she will do it again," she told the newspaper.

Republicans currently hold 51 seats in the Senate. The GOP's odds of losing control of the chamber appear slim at this point: Democrats have to defend 26 seats in this year's elections, versus only eight for Republicans.

Several Democrats face re-election in states Trump won in 2016 including North Dakota, Missouri, West Virginia, Indiana, Pennsylvania and Ohio.