Sen. John Kennedy, R-La., said the Russia investigation was "over" despite congressional Democrats' efforts and the release of Special Counsel Robert Mueller's letter, which he deemed "much ado about nothing."

"A lot of people got their bowels in an uproar over it. It turned out to be much ado about nothing," Kennedy said while appearing on "Your World with Neil Cavuto" on Wednesday.

He was referring to a letter in which Mueller expressed his dismay with the way that Attorney General William Barr described the special counsel's report on the long-running Russia investigation. Although Mueller said he wanted Barr's March summary to more better capture the "context, nature, and substance" of his report, he said during a phone call between the two that he wasn't calling the summary "inaccurate."

The release of Mueller's letter came just before Barr's Senate testimony on Wednesday and at the end of a long, multiyear investigation in which some critics said President Trump had colluded with Russia during the 2016 presidential election and tried to obstruct the government's probe into the matter. Barr's summary denied Mueller had found sufficient evidence on either front.

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"So, my question was real simple, Has Mr. Mueller changed his mind? Has he changed his conclusions?" Kennedy said, noting Mueller's dissatisfaction with Barr's summary. "He has not changed his mind," said Kennedy, who is on the Senate Judiciary Committee.

During Barr's testimony, he faced intense criticism from cable news and politicians, along with some calls for his resignation. Those calls, according to Kennedy, were "patently absurd."

"Many of my Democratic friends ... are not in good faith. I mean, Trump could come out tomorrow solidly in favor of children and prosperity and they would say he's wrong."

Following the Mueller report, Democrats pushed for more information related to the obstruction concerns that Mueller outlined in his report. "This is the theory of the case now for some of my Democratic friends: Trump covered up a crime that nobody committed," Kennedy said.

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"This thing is over. It's over," he added. "They threw everything they had at the president ... it was cross between an endoscopy and a colonoscopy, and here's what they said: 'No indictment.'"

White House senior adviser Kellyanne Conway similarly told Fox News that the Russia investigation was a "political proctology exam" and requested that Rep. Adam Schiff, D-Calif., a prominent figure in Congress' investigatory efforts, resign from his role as House Intelligence Committee chairman.