Washington (CNN)Tennessee Republican Sen. Bob Corker on Thursday withheld an endorsement for President Donald Trump's re-election bid, adding that it is "questionable" whether Trump will even seek a second term in office.
Corker questions Trump candidacy in 2020
"I have no idea whether the President will run for re-election nor what the field will be on the Republican side, so I think it's way too early to weigh in on who won my support," Corker told CNN's "New Day" co-anchor Alisyn Camerota.
"But are you saying you're not sure the President is going to run?" Camerota asked.
"I'm definitely not sure if he's going to run," Corker replied.
"Here's what I'm getting at: If he's the nominee, will you support him?" Camerota followed up.
"Again, if he's the nominee, you mean he's won the primary?" Corker said.
"If he runs for re-election, are you going to support him?" Camerota asked again.
"Well, I want to know who else is in the field," Corker said, later adding that once he knows who is officially running, he will announce who he will support. Corker said he has "no idea" who might join the race.
The Tennessee senator added that Trump may be putting on appearances of a re-election bid so as to avoid being viewed as a lame duck president, but offered no evidence to support his claim.
Although Corker was at one point being considered for Trump's Cabinet, when he announced his retirement from the Senate last year, Trump tweeted that the Tennessee senator "begged" him for an endorsement and decided not to run because he "didn't have the guts." Corker, in turn, called the White House an "adult day care center."
Sources told CNN that the two had patched things up earlier this year, but Corker has continued to speak out. Earlier this week, he said there was "constant chaos" at the White House and blamed Trump's selection of "unconventional" advisers.
Despite Trump's formal re-election efforts, a growing list of Republicans on Capitol Hill are staying mum on their support of his bid.
CNN reported Thursday that Senate Majority Whip John Cornyn, Tennessee Sen. Lamar Alexander and South Carolina Rep. Mark Sanford are among the Republicans who are holding out their official support for Trump in 2020.
Wisconsin Sen. Ron Johnson also refused to endorse the President, telling "New Day" earlier Thursday that "it could be a completely different world by 2020."