WASHINGTON — President Donald Trump’s claim of exoneration in the Russia investigation was undercut Sunday by several Republican lawmakers, including one who helped draft a controversial memo the president has embraced, alleging the FBI abused its surveillance powers.

Rep. Trey Gowdy of South Carolina said in an interview on CBS’ “Face the Nation” that the memo, spearheaded by the chairman of the House Intelligence Committee, Rep. Devin Nunes, R-Calif., did not have “any impact on the Russia probe.”

Gowdy is a member of the committee and the only Republican on it who’s read classified documents that are the basis of the disputed four-page memo.

On Saturday, Trump had seized on the GOP memo, which was publicly released Friday after he’d declassified it over Justice Department objections, as confirming his repeated contention that the investigation led by special counsel Robert S. Mueller III is a “witch hunt.” In a tweet from his Florida resort, the president declared the memo “totally vindicates” him.

Even before seeing it, the president also reportedly told associates the memo bolstered the case for ousting Deputy Attorney General Rod Rosenstein, a Trump appointee who oversees Mueller. Democrats as well as some Republicans have warned such a move could spark a constitutional crisis.

Gowdy, a former federal prosecutor, said the material the FBI used to win a secret surveillance court’s approval for its surveillance of former Trump campaign associate Carter Page did not prompt the bureau’s wider look at whether the Trump campaign colluded with Russia to influence the 2016 election. Gowdy, who has announced plans to retire, also said he supports Mueller “100 percent” in conducting the investigation.

A fellow Republican congressman, interviewed on CNN’s “State of the Union,” also said the overall Russia investigation is a “separate issue” from matters addressed in the memo.

“It’s more looking within the agencies, something we have oversight over,” Rep. Brad Wenstrup of Ohio said.

A third Republican on the committee, Rep. Will Hurd of Texas, also said he disagreed the memo bolsters the case the White House has been making for months against the impartiality of Mueller.

“I don’t believe this is an attack on Bob Mueller,” Hurd said on ABC’s “This Week.” Hurd, who formerly worked for the CIA, added, “I would say that (the Justice Department) should continue doing their job.”

The comments from Hurd, Gowdy and Wenstrup were not only a break with Trump’s stance, but with that of many House Republicans who’ve suggested the entire investigation is corrupted. The three lawmakers reflected the more measured stance of House Speaker Paul D. Ryan, who insisted Friday the memo isn’t “an indictment” of the FBI and Justice, nor does it “impugn” Mueller’s investigation or Rosenstein.

Democrats again decried what they call Nunes’ politicization of intelligence in the memo’s release, saying Trump’s allies inappropriately were trying to use it to discredit Rosenstein and by extension Mueller.

“It is the duty of Congress to focus on the Russia investigation” and not cherry-pick facts in a bid to exonerate the president, Senate Minority Whip Richard J. Durbin of Illinois said on CNN.

“The information, the facts, tell a totally different story” than the narrative put forth by Nunes with the support of Republicans on the Intelligence Committee, Durbin said.

Nunes has come under heavy criticism from some former intelligence community leaders, including ex-CIA director John Brennan, who on Sunday termed the memo “appalling.” Speaking on NBC’s “Meet the Press,” Brennan said Nunes had “abused the chairmanship” of the House Intelligence Committee.

The committee’s ranking Democrat, Adam B. Schiff of California, who is trying to win public release of a 10-page Democratic rebuttal to the memo, on Sunday said the Nunes-backed document was not a legitimate attempt to exercise congressional oversight of law enforcement.

“The interest wasn’t oversight,” Schiff said on “This Week.” “The interest was a political hit job on the FBI in service of the president.”

A former senior Trump aide, meanwhile, disputed news reports that the president had ordered Mueller fired last year but was dissuaded by White House counsel Don McGahn, who threatened to quit rather than carry out the order.

Former White House Chief of Staff Reince Priebus, who was pushed out in July, was still at his post in June when Trump was reported to have given the order. Priebus, interviewed on “Meet the Press,” said he “never heard” of any such contention.

“I never felt that the president was going to fire the special counsel,” Priebus said.

Many associates have implored Trump to stop talking and tweeting about the Mueller investigation, fearing his public statements offer ammunition to the special counsel in building a case of obstruction of justice.

Last month, the president startled aides with an off-the-cuff declaration to reporters that he was willing to be interviewed under oath. His lawyers quickly stepped in to say that would need to be negotiated.