Barr's confirmation hearing just kicked off, and he's already gone against Trump in big ways

• Attorney General nominee William Barr on Tuesday went against President Donald Trump in significant ways early on in his confirmation hearing.
• Barr rejected Trump's perception and characterization of several issues, from special counsel Robert Mueller's investigation into Russian election interference to the president's pardon powers.
• "I don't believe Mr. Mueller would be involved in a witch hunt," Barr said as he was questioned by the Senate Judiciary Committee.

Within the first two hours of Attorney General nominee William Barr's confirmation hearing on Tuesday, he had made significant breaks from President Donald Trump.

Barr made it clear he does not agree with the president on array of issues, perhaps most notably special counsel Robert Mueller's investigation into Russian election interference and the Trump campaign's alleged collusion.

The former attorney general, who seems poised to be confirmed and get his old job back, rejected Trump's characterization of the Mueller probe as a "witch hunt."

Read more: William Barr: Mueller and I are 'good friends' and 'I don't believe' he 'would be involved in a witch hunt'

"I don't believe Mr. Mueller would be involved in a witch hunt," Barr said as he was questioned by the Senate Judiciary Committee.

Barr, who has a personal relationship with Mueller, also said he would allow the special counsel to finish the investigation if he's confirmed as attorney general.

Trump has repeatedly called for the investigation to end, and apparently even sought to have Mueller fired but ultimately backed down after senior White House officials vehemently objected.

Read more: William Barr says in prepared testimony that Mueller should be allowed to 'complete his work' on the Russia probe

Barr also said he believed former Attorney General Jeff Sessions was correct to recuse himself from the Russia investigation, a move that outraged Trump and led to his deteriorating relationship with Sessions.

Sessions ultimately resigned at the request of the president last November after repeatedly being publicly lambasted by Trump on the recusal issue.

In his opening remarks, Barr also seemed to take a veiled jab at Trump's attacks on the Department of Justice, arguing it should not be politicized in any context.

Read more: Rudy Giuliani doubles down on his dubious claim that the White House should be able to review and correct Mueller's report before it's released

"In the current environment, there are places in the government where the rule of law - not politics - holds sway... The Department of Justice must be that place," Barr said.

Trump has at times claimed he has virtually unlimited power to pardon people as president -including himself. This has been a point of concern surrounding Mueller's investigation and Trump associates who've landed in legal trouble, particularly his former campaign chairman Paul Manafort.

During Tuesday's hearing, Barr rejected the notion Trump has a blank check to use the pardon power. Democratic Sen. Patrick Leahy asked Barr if a president could offer a pardon in exchange for a witness promising not to incriminate the president.

Barr told Leahy: "No, that would be a crime."