Sen. Bob Corker (R-TN), who announced last September that he would retire at the end of this term, is flirting with the idea of un-retiring.

Corker is reportedly “listening” to some Republican colleagues encouraging him to run for reelection, according to Politico, amid concern that the party’s leading candidate, Republican Rep. Marsha Blackburn, could lose the Tennessee Senate seat to a Democrat in the 2018 midterms.

Blackburn, who launched her bid for Corker’s seat last October with a clear conservative message against congressional Republican leadership, fell behind former Democratic Gov. Phil Bredesen in a hypothetical matchup poll. The internal poll, conducted by Glen Bolger of the Republican research firm Public Opinion Strategies and obtained by Politico, showed Bredesen up 47 to 45.

Blackburn, who announced her bid reflecting Trump’s messaging, and Corker, who went on a tirade against the president last year, represent the two often competing sides of the Republican Party. If Corker does choose to get back into the race, he faces a serious risk of losing the primary; the base hasn’t abandoned Trump, especially in a state he won by 26 points, but general election voters are increasingly looking like they might.

An open contest always carries a risk for the incumbent party. If Corker decides to jump back into the race, it will only get messier. As rumors circulate, Corker has remained quiet, declining to comment on multiple occasions Monday.

This midterm cycle, the Senate election map generally favors Republicans. A Democratic win in Tennessee would be unmitigated disaster.

Meanwhile, Corker has toned down his feud with Trump

Only six months ago, Corker was making headlines for saying members of Trump’s administration had the potential to send the nation into “chaos,” and referring to the White House as an “adult day care center” for Trump. He warned that Trump was setting the United States on the “path to World War III.”

It led to some hot-headed exchanges between Trump and Corker, the chair of the powerful Senate Foreign Relations Committee. Trump lashed out, calling the Tennessee Republican “Liddle” and saying Corker “begged” for Trump’s reelection endorsement. (There are reports saying the opposite happened.)

Corker’s comments were largely assumed to be those of a man on his way out, free to say what he really feels.

But in recent months, Corker has toned down his rhetoric. When Trump was threatening North Korean leader Kim Jung Un on Twitter about the size of his “nuclear button,” Corker refused to comment. He later told Vox that his close relationship with Secretary of State Rex Tillerson and Secretary of Defense James Mattis had put his concerns about national security at ease.

Corker has been a reliable vote for the Republican Party and hasn’t stood in the way of any major Trump legislation — even voting for the tax bill, which he initially opposed on the grounds that it would increase the deficit. (Although as chair of the Senate Foreign Relations Committee, he did push for the sanctions bill against Russia that Trump was not pleased with.) But there’s no question that if he wants to run for reelection, his comments on Trump will follow him.

Blackburn is currently the clear Republican favorite, and she’s not going anywhere

Blackburn, meanwhile, who currently represents a deeply red Tennessee district in the House — one that went for Trump by almost 40 points in the 2016 election — is positioning her platform in close alliance with the White House, even if it means putting herself at odds with the Republican establishment in Congress.

“The United States Senate, it’s totally dysfunctional and enough to drive you nuts,” Blackburn said of the Republican-led upper chamber in the first lines of a video announcing her candidacy.

She has framed herself as an anti-establishment conservative — a close supporter of Trump, his anti-immigration message, and the right’s stand against “political correctness.”

It’s been working so far. She’s the clear favorite in the Republican primary field in Tennessee, out-polling former Rep. Stephen Fincher, who has gained more support from the moderates, and raising $2 million in her first quarter — a serious fundraising effort.

Her campaign says she has no intention of dropping out of the race.

“It’s well past time for the good old boys’ club in Washington, D.C., to quit thinking they know who the best candidate and conservative leader is for Tennessee families,” Andrea Bozek, a spokesperson for Blackburn, told Politico.

But the run from former two-term Gov. Bredesen, who was the last Democrat to win statewide office in Tennessee, is giving Democrats hope they can make what would otherwise be an incredibly tough race into a competitive fight.

Correction: A previous version of this story said the poll from Glen Bolger had “a sample that was overweighted with Republicans.” It had a GOP oversample for the primary questions — not for the general election. We regret the error.