Sen. Chuck Grassley Charles (Chuck) Ernest GrassleySenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE (R) at a town hall in his home state of Iowa on Friday repeatedly dodged questions from his constituents on President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE's behavior following reports that Trump referred to Haiti, El Salvador and African nations as "shithole countries."

“Are you not personally concerned about his fitness to serve? If not, why not? Because I’m very concerned,” one attendee told Grassley, who responded by saying he was not qualified to make a psychological assessment, the Des Moines Register reported.

The GOP senator also refused to answer questions about the president's use of Twitter.

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“I’m not president of the United States. I’m a check on the president of the United States. That’s my constitutional responsibility. I’m going to do what I can under our constitution to make sure that nothing bad happens to our country," he said.

Questions surrounding the president's mental health bubbled up last week after author Michael Wolff said in his new book "Fire and Fury: Inside the Trump White House" that White House staff have questioned Trump's fitness for office.

One constituent at Grassley's town hall on Friday also challenged the Senate Judiciary Committee chairman for "sliding" on the Russia investigation, accusing him of "protecting the president" and "shifting the attention away from Russia," according to the Register.

Grassley responded by explaining his rationale for issuing a criminal referral for Christopher Steele, the former British intelligence agent behind a dossier of unverified allegations linking Trump to Russia.

Grassley did respond Friday to Trump's reported comments on Haiti, El Salvador and African nations, which have sparked outrage on both sides of the aisle.

“I think it detracts from the very important issue we’ve got to get solved by March 5,” Grassley said, according to the Register.

He was referring to the deadline for lawmakers to provide a legislative fix for immigrants affected by Trump's decision to rescind the Obama-era Deferred Action for Childhood Arrivals (DACA) program, which provides protections to certain immigrants who were brought to the country illegally as children.

“I think, generally speaking, that you’re better to keep to the issues, don’t do anything to detract from the issues and, bottom line, all people ought to be treated with respect," Grassley added.

Trump denied in a tweet Friday that he said "anything derogatory" about Haitians during his meeting the previous day with lawmakers after The Washington Post and other outlets reported his "shithole" remark.