Four members of the House have said they won't run for reelection and two senators are now weighing their options. (Sarah Parnass/The Washington Post)

Sen. Bob Corker (R-Tenn.) is considering whether to run for reelection or retire, he said Monday, drawing fresh attention to a dilemma with far-reaching implications for his party.

Corker is an influential Republican who at times has clashed with President Trump. If he retires, it would probably put a seat that analysts expect to stay in GOP hands into a more uncertain state. It would also mark the end of the tenure of a well-respected member of the Republican Party’s mainstream governing wing, which has frequently collided with Trump and his nationalist, populist allies.

Corker’s latest input came on the same day that a fourth House Republican representing a closely divided district targeted by Democrats said that he intends to retire from Congress. Rep. Dave Trott (R-Mich.) said in a statement that he would not seek another term representing his suburban Detroit district, having decided “that the best course for me is to spend more time with my family and return to the private sector.”

Corker, chairman of the Senate Foreign Relations Committee, said in a statement that it has been “a tremendous privilege to serve Tennesseans in the Senate” but added that he was “still contemplating” his electoral future.

“I think everyone in the Volunteer State knows, as they did in 2012, that running for reelection has never been an automatic for me,” he said.

He told reporters later Monday that his decision will be personal one, rather than a reaction to the broader political and governing environment, which he said “ebbs and flows.” And he voiced confidence the Trump administration was not trying to defeat him.

“I have no reason whatsoever to believe the administration would encourage a primary,” he said.

Corker’s statement and comments came after an interview he did with CNN last week — in which he raised the prospect of ending his Senate career — was published Monday morning.

After President Trump's most recent rhetoric about Charlottesville inflamed even more criticism, many Republicans stayed silent. But a handful of GOP lawmakers and now Trump's own economic adviser are directly criticizing him. (Jenny Starrs/The Washington Post)

Democrats are defending more than twice as many Senate seats as Republicans this election cycle, including several in conservative-leaning states that Trump won. This has given Republican strategists some confidence about potentially expanding their 52-to-48 majority in the upper chamber.

However, in some races, including Tennessee, Trump, his allies or both have signaled that they may get behind a challenger to the Republican incumbent, complicating the Senate GOP midterm outlook. Some strategists worry that competitive and nasty primaries could consume financial resources and produce challenger nominees who would be less competitive in the general election than the incumbents.

Corker has on occasion been outspoken in his criticism of Trump. He recently expressed displeasure with the president’s response to the deadly violence in Charlottesville and warned that if Trump does not change his behavior, “our nation is going to go through great peril.” Corker said Trump had not demonstrated the “stability” or “competence” necessary to effectively lead the nation.

The following week, Trump took aim at Corker on Twitter, writing: “Strange statement by Bob Corker considering that he is constantly asking me whether or not he should run again in ’18. Tennessee not happy!”

Corker did not mention Trump in his statement Monday. But the possibility that Corker could face resistance from the president or his allies in the Republican primary, given Trump’s open animosity, has loomed over the contest.

The Trump-Corker relationship has been more positive at times in the past. Trump had considered Corker as a possible vice-presidential running mate and secretary of state.

One Republican in close contact with Corker’s team, speaking on the condition of anonymity to be candid, expressed confidence Monday that Corker will run for a third term. But in his statement, the senator suggested he was genuinely torn.

“After spending a lifetime in business, I ran for mayor of Chattanooga as a civic endeavor, and I continue to do what I do because I wholeheartedly believe in public service,” Corker said. “That approach allows me to truly throw myself into the job and make decisions based on what I believe is best for Tennessee and our country without thinking about the next election or the next potential opportunity.”

According to his most recent campaign finance report, Corker had more than $6.5 million in his campaign account, a substantial sum. A Republican with direct knowledge of the situation granted anonymity to relay a figure that had not been announced said Corker now has $7.5 million. The nonpartisan Cook Political Report rates the Tennessee Senate race as “solid Republican.”

Trott’s decision, meanwhile, follows announcements from Reps. Charlie Dent (R-Pa.), Dave Reichert (R-Wash.) and Ileana Ros-Lehtinen (R-Fla.), all of whom represent competitive districts that Democrats are targeting in the 2018 midterm elections.

Michigan’s 11th Congressional District, comprising parts of suburban Wayne and Oakland counties, has a slight Republican lean. Trump won the district by four points in November; Mitt Romney won it by five points over Barack Obama in 2012. But two key House forecasters on Monday immediately moved the seat from a likely Republican hold to a toss-up.

A spokeswoman for the Democratic Congressional Campaign Committee, Rachel Irwin, said Monday that the district is “trending toward Democrats” and that Trott’s retirement “is a telltale sign that running for reelection in Paul D. Ryan’s do-nothing Congress would have been an uphill climb not worth the effort.”

At lease one serious Democratic candidate has entered the race: Haley Stevens, a Michigan native who worked in the Obama administration’s auto industry rescue effort.

Rep. Steve Stivers (R-Ohio), chairman of the National Republican Congressional Committee, praised Trott in a statement Monday and said GOP political leaders “will not let his hard work go to waste, and are confident this seat will remain under Republican control.”