CNN host Michael Smerconish on Monday said Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) is "planting seeds" to call into question President Trump's fitness for office.

"I'm thinking of the 25th Amendment, Section Four, which speaks to a president who's unable to discharge the powers and duties of his office," Smerconish said on CNN.

Smerconish cited some of the comments Corker has made, saying the Tennessee Republican has used words in the past such as "reckless" and "chaos" when talking about Trump.

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"Now he's saying that 'he concerns me,' " Smerconish said.

"I think he's planting seeds for questioning the fitness — the mental fitness of the president, pursuant to the 25th Amendment, to continue with his responsibilities."

Smerconish was pressed on whether he thinks Corker is that deliberate in his comments.

"If you were to take a look at the amendment and then say, OK, how would you make an argument, what sort of things would you say in making a case to fulfill Section Four of the 25th Amendment," he said, "those words would be at the top of the list."

His comments come amid escalating tensions between Trump and Corker.

Trump took aim at Corker on Twitter over the weekend, saying Corker begged for his endorsement for reelection to the Senate but Trump declined the request.

Corker, who is not running for reelection, blasted Trump in response, saying the White House has become an "adult day care center."

In an interview in The New York Times on Sunday, Corker said Trump's threats to other countries could put the U.S. "on the path to World War III."

"He concerns me," Corker told the Times.

"He would have to concern anyone who cares about our nation."