Former FBI Director James Comey is a “proven liar” and Attorney General Jeff Sessions “didn’t step up” to shut down an “unjustifiable investigation.” Those were just two of the claims made Friday by Rudy Giuliani, one of President Donald Trump’s lawyers, as he continued an escalating effort to erode the legitimacy of the Justice Department’s Russia probe.

As Special Counsel Robert S. Mueller III and his team continue their probe of Russian meddling in the 2016 U.S. election, possible coordination with the Trump-Pence campaign, and whether the president obstructed justice, Giuliani — joined by Trump and others — are executing a strategy intended to raise doubts about the necessity of the investigation, whether Mueller and the FBI are out to get Trump, and the special counsel’s tactics.

The former U.S. attorney and New York mayor lashed out at Sessions, Comey, Mueller and others Friday morning during a sometimes-explosive interview with CNN’s Chris Cuomo. Among other charges, Giuliani said those conducting the probe are guilty of crimes against Trump.

“If you’re asking me who has commited crimes here, the crimes have been committed by the investigators. Illegal leaking, lying about relevant matters, invasions of attorney-client privilege — which is unethical, not illegal,” the president’s attorney said. That came after Giuliani said a dossier compiled by a former British spy about then-businessman Trump’s activities — some salacious and embarrassing — in Moscow, as well alleged contacts with Russians during the 2016 campaign cycle was “corrupt.”

Since Giuliani’s addition, the president’s personal legal team has attempted anew to build a narrative that the investigation was launched on legally wobbly grounds, including being based largely on the “Steele dossier,” which Trump’s team claims was paid for directly by Democratic Party officials.

Watch: FBI Director Says Trump Didn’t Seek Advice Before Tweeting on ZTE

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But the Trump team’s claim excludes any mention that an unknown Republican client paid for research firm Fusion GPS to explore Trump’s Russia ties even before the Hillary Clinton campaign and the Democratic National Committee inquired about retaining its services. That undercuts their claims that the dossier was produced via purely partisan efforts. Giuliani also excluded that fact Friday morning.

Attacks on the dossier and those at the top of the Justice Department are intended to rally public support around Trump by casting him as a victim.

“How about what Jeff Sessions did to him? What Jeff Sessions has done to him is to stick him with a special counsel because he didn’t step up and say ‘I can make this decision,’” Giuliani said Friday of the attorney general, who recused himself from the Russia probe due to contacts he had with a Russian official as a senator who was advising the Trump campaign.

“He didn’t uphold the Constitution,” Giuliani said of Sessions. “You don’t need a special counsel in this case.” He also contended that Deputy Attorney General Rod Rosenstein, nominated for the post by Trump “should be handling the case.” It was the deputy AG who appointed Mueller — but only after the president fired then-FBI Director Comey and admitted the Russia probe was on his mind when he decided to do so.

The Trump team also is attempting to erode public confidence — polls show a majority of Americans want Mueller to conclude his investigation — in the special counsel’s work. Another line of attack is that Mueller is angling to trick Trump into committing perjury.

“And explain to me why they even need an interview with the president if it isn’t to trap him into perjury, which is what the judge in the [Paul] Manafort case has said that they’re trying to trap people into perjury,” Giuliani said Friday.

“A perjury trap is when you get someone to lie about what you’re telling the truth,” he said. Giuliani believes he has identified whom that “someone” would be.

“You’ve got Comey coming forward who will lie. They will believe Comey over him,” Giuliani said of his Oval Office-occupying client. “Lying is black and white. The president isn’t going to lie, let’s get that straight.”

Giuliani’s strategy was clear during his back-and-forth with Cuomo: Use “Comey” and “liar” as many times as possible in the same sentence.

“If we’re going to talk about liars, let’s talk about Comey, who is a proven liar,” he said. “That’s the guy they are going to trust over the president.”

His strategy is to raise doubts about Comey as a reliable witness; the former FBI director already has spoken with the special counsel’s team.

[Fact Check: Trump’s Dossier Tweet Full of Dubious Claims]

The president has said he would like to testify and take questions from Mueller and his team. Two of his former lawyers, John Dowd and Ty Cobb, advised him against doing so, though. Both recently left his personal and White House legal teams. Giuliani came onboard saying part of his job would be to negotiate an interview, but one still seems a long shot — and Giuliani says that’s because Trump would not get a fair shake in a probe that reached a conclusion before it even started.

“The president would testify tomorrow if it was about the truth,” he said. “The truth is he had nothing to do with Russia. I was on that campaign. He didn’t talk to Russians. He had nothing to do with Russia.”

He also echoed Trump’s Thursday contention that a FBI informant inside the Trump campaign illegally spied on him and his associates. Giuliani deflected a question about that on Friday, instead pointing to reporting by the New York Times that no evidence of collusion has been uncovered. The president was back making the claim Friday morning, labeling use of the “spy” as “Really bad stuff.”

“Apparently the DOJ put a Spy in the Trump Campaign. This has never been done before and by any means necessary, they are out to frame Donald Trump for crimes he didn’t commit.” David Asman @LouDobbs @GreggJarrett Really bad stuff!

— Donald J. Trump (@realDonaldTrump) May 18, 2018

Trump on Friday charged the alleged informant began working with the FBI before the Russia probe started. If true, the president said it would be the biggest scandal in American political history. (He often makes such grand pronouncements without supporting context or data.)

Reports are there was indeed at least one FBI representative implanted, for political purposes, into my campaign for president. It took place very early on, and long before the phony Russia Hoax became a “hot” Fake News story. If true – all time biggest political scandal!

— Donald J. Trump (@realDonaldTrump) May 18, 2018

Notably, Giuliani did not shy away from questions about Trump possibly facing criminal charges. But his replies were aimed at building a narrative that a sitting president cannot be charged with crimes in the legal realm.

He claimed, citing a Justice Department memorandum, that federal officials “cannot indict the president. Nor can you [conduct] a criminal process involving the president.” Legal experts and lawmakers, however, say there is no firm legal conclusion on either matter.

“No president has ever complied with a subpoena,” Giuliani said even though he said during then-President Bill Clinton’s legal troubles in 1998 that Clinton would have to comply with a subpoena to testify in his case.

The Trump team’s argument can be boiled down to two sentences uttered by Giuliani on Friday morning: He said the Justice Department has “wasted $20 million on an investigation that begins without any evidence and ends without any evidence.” Soon after, he said of the special counsel’s and media’s perception of those involved: “Anyone who defends the president is some kind of scoundrel, and anyone who lies about him is okay.”