(CNN) A defiant Sen. Lindsey Graham said Monday that President Donald Trump should ignore congressional subpoenas demanding the administration turn over records to Capitol Hill, even though the South Carolina Republican once noted a similar fight had contributed to Richard Nixon's downfall.

Graham, who played a prominent role in President Bill Clinton's impeachment proceedings in 1998, defended his past stance in an interview with CNN on Monday, while calling on Trump to "fight like hell" against House Democratic "political hacks" and goading Democrats to carry through with impeaching Trump if they want.

And when asked about Trump's behavior, specifically the 10 instances documented in special counsel Robert Mueller's report of the President's possible obstruction of justice, Graham said bluntly: "I don't care."

"There were zero instances of Trump impeding Mueller," Graham said. "Zero."

But Graham, while then a member of the House of Representatives in 1998, took to the floor during the Clinton impeachment proceedings and made reference to the Watergate scandal, which ended Nixon's presidency, noting that Nixon "failed" to answer a subpoena and that was "the day he was subject to impeachment because he took the power from Congress over the impeachment process away from Congress."

Nixon ignored subpoenas from special prosecutor Leon Jaworski before being ordered by the Supreme Court to turn over his taped recordings with staff.

Asked about his past quote, Graham first said, "I said that?" before adding that Nixon "must not have cooperated with the special counsel" and House Democrats are now engaging in a "political exercise and they won't let it go."

"Their guys are political hacks right now," Graham said, before referring to House Democratic chairmen, including Jerry Nadler, the New York Democrat who runs the House Judiciary Committee. "Mueller was the guy I was looking to -- not Nadler, not Lindsey Graham, not any of us, not a Republican."

In 1998, House Republicans including Graham voted for an article of impeachment saying Clinton "impaired the due and proper administration of justice" and "refused and failed to respond to certain written requests for admission and willfully made perjurious, false and misleading sworn statements" in describing his relationship with White House intern Monica Lewinsky. The Senate acquitted Clinton of all charges.

When asked if he treated Trump differently than he would a Democratic president, Graham said his "record is clear" because he was the only Republican who broke with his party to vote in committee against one of the articles of Clinton's impeachment regarding lying in a civil case.

In the interview, Graham said a crucial distinction between Trump and Clinton was that the former did not obstruct justice while "Clinton did." He argued Trump "fully cooperated" with the special counsel, even though Mueller was unsatisfied with the President's written responses and unsuccessfully sought an in-person interview with Trump.

"The President didn't have to talk to him," Graham said of Mueller when asked about the special counsel considering Trump's written responses inadequate. "And if he wanted more he could have gone to court but he chose not to. It's over."

Mueller's report detailed multiple possible episodes of obstruction in which the President had sought to end the FBI and special counsel probes of Russian interference in the 2016 election through intermediaries. But Mueller concluded, "The President's efforts to influence the investigation were mostly unsuccessful, but that is largely because the persons who surrounded the President declined to carry out orders or accede to his requests."

Democrats now plan to fully probe the incidents of potential obstruction, even though Attorney General Bill Barr has concluded that Mueller found insufficient evidence that the President committed such an offense.

Graham defended Trump's vow to fight all congressional subpoenas.

"I'm OK with a politician fighting another politician," Graham said. "And that's what this is. The Mueller report is the last and final word on everything (about) Trump's campaign for me."

"Obstruction of justice to me is absurd because the President cooperated fully," he added. "So if the House wants to keep doing this, if I were the President I'd fight like hell."

Graham has said he has no interest in allowing Mueller to testify in public about the report. Asked why not, he said: "I don't care to hear from Mueller. I've heard from Mueller through his report."

Graham's comments are the latest sign of his evolution from Trump detractor to one of his staunchest defenders. During the 2016 presidential campaign, Graham said Trump was "not a conservative Republican" but "an opportunist." "He's not fit to be President of the United States," tweeted Graham.

But since Trump became President, Graham has become a crucial ally, coming to Brett Kavanaugh's defense when the Supreme Court nominee's confirmation was imperiled by claims of sexual assault. Kavanaugh ultimately squeaked by on a 50-48 vote.

Graham, who is running for reelection in 2020, is now the chairman of the Senate Judiciary Committee and would play a crucial role should the Democratic-controlled House decide to impeach the President and try the charges in the Senate.

In the interview, Graham's message seemed to be: Bring it.

"My advice to Democrats: If you think President Trump did something wrong that you need to cleanse the office -- do it," Graham said.