Former Attorney General William Barr said the Durham report has vindicated former President Donald Trump against years of allegations of Russian collusion but stopped short of supporting another term for him in the White House.

"I think [the Durham report] helps him in the short term. My own view is that he will not win the nomination," Barr said Tuesday on "Special Report." "And I have nothing personal against him… But I just don't think he's the right leader for the Republican Party going forward. I think people who want to restore America should look for a big victory that brings strength into the Congress and allows us to achieve some fundamental changes. And I don't think he's capable of delivering that kind of victory."

Barr, who also served as the nation's top lawman under President George Herbert Walker Bush, said Special Counsel John Durham's probe was a success in that it revealed the truth, dismissing contentions that its intention was that of a typical criminal investigation like the one launched against Trump that was headed by former FBI Director Robert Mueller

"I take away from it that it was a success in that its purpose from the very beginning was to get to the truth. It was not launched as a criminal investigation. And people who compare it to the Mueller investigation are simply wrong," Barr said.

Barr said he asked Durham to "get to the bottom of" the origins of the Russia investigation, and told him that any crimes found should be prosecuted but that the prime goal was to substantiate how the Trump inquiry was launched.

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Durham-Trump-Clinton split

John Durham, Donald Trump, and Hillary Clinton (Associated Press)

"[Durham has] dug into it, and I think he's gotten as close to the bottom as anyone is going to get to this," he said.

Barr said the probe found Hillary Clinton's 2016 campaign launched a "smear" offensive based on finding Russian sources to undermine Trump by spreading potentially false information to the FBI as well as the media.

"Both the press and the FBI abandoned any semblance of professionalism and took up the cause with a vengeance," he contended. "And I think the real story here from the FBI's perspective is what an abomination this was, this so-called investigation. It wasn't a witch hunt, it's a damn good imitation of one."

Barr said Mueller "came up empty" against Trump and instead had to essentially settle for more minor indictments of two Trump-connected Republican political consultants – Roger Stone and Paul Manafort.

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Bill Barr

William P. Barr (Michael Reynolds-Pool/Getty)

"But there was no collusion [with Russia]," Barr underlined, adding Congress and ultimately the FBI must follow through and enact changes to prevent such behavior.

He said the problems at the bureau were all among the top brass at the time, Director Jim Comey, his deputy Andrew McCabe, and agent Peter Strzok.

Barr told "Special Report" that the current director, Christopher Wray, has made some of the appropriate changes at the J. Edgar Hoover Building.

Barr said Trump executed "great policies" while in office. The fact Trump was able to effect sweeping positive changes and policies while dealing with unending investigations is a testament to his tenure, the former attorney general argued. 

"[Trump] deserves a lot of credit for what he accomplished. And this [Russiagate] was a grave injustice. And the fact that he was able to accomplish a lot in the face of it, I think was a great achievement," Barr said.

Still, he said he will not support him for the 2024 GOP nod.

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Donald Trump speaking in Iowa

Donald Trump (Scott Olson/Getty)

When asked if he believes Trump would lose, Barr said his former boss has the "best chance" of defeat against President Biden. A Trump nomination, he added, would risk down-ballot losses because of his name at the top of the ticket, characterizing the dynamic as one of voters turning out not to vote for Democrats but instead against Trump.

He said Trump is unable to unify the GOP in the way he "stopped the progressive march" in 2016.

For his part, Trump has repeatedly lambasted Barr, characterizing him as a RINO who "did not have the courage or stamina" to fight for "election integrity," while separately calling his fellow New York native "slovenly."