Attorney General William Barr fired back Wednesday at Democrats who for weeks have called his integrity into question over his handling of Special Counsel Robert Mueller’s Russia report, suggesting during a testy Capitol Hill hearing they were only using the issue to score political points ahead of the 2020 election -- and advising that the DOJ's role in the controversy is now "over."

“We have to stop using the criminal justice process as a political weapon,” Barr said during a back-and-forth with Connecticut Democratic Sen. Dick Blumenthal.

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The exchange was one of several heated moments during Barr's first hearing -- before the Senate Judiciary Committee -- since the release of the Mueller report. The testimony covered everything from Barr's decision not to pursue an obstruction case against President Trump to process delays in getting a redacted version of Mueller's report to the public to Mueller's apparent concerns about how Barr initially relayed his findings to Congress.

The dust-up with Blumenthal came after the senator told Barr "I think history will judge you harshly” and accused him of using his summary of Mueller’s probe to exonerate Trump of obstruction of justice. The senator called Barr the “fall guy for this report."

“I didn’t exonerate,” Barr replied. “I said that we did not believe that there was sufficient evidence to establish obstruction.”

Barr continued: “The job of the Justice Department is now over… the report is now in the hands of the American people. Everyone can decide for themselves. There’s an election in 18 months – that’s a very democratic process. But we’re out of it.”

The clashes with senators only escalated from there during the final couple hours of the hearing, as partisan tensions flared and Barr's impatience with the lines of questioning began to show.

Minutes later, Hawaii Sen. Mazie Hirono accused Barr of lying to Congress and told him he should resign.

"Mr. Barr, now the American people know that you are no different from Rudy Giuliani or Kellyanne Conway or any of other people who sacrifice their once decent reputation for the grifter and liar who sits in the Oval Office," Hirono said.

Eventually, the Republican chairman of the committee, South Carolina Sen. Lindsey Graham, stepped in to cut Hirono off.

"You slandered this man from top to bottom," Graham told the Hawaii senator.

Another Republican senator, Texas Sen. Ted Cruz, told Barr he was being subjected to "Kavanaugh-level" slander by Democrats -- in reference to the highly contentious hearings last year of Supreme Court Justice Brett Kavanaugh.

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At another point during the hearing, Barr flatly rejected a Democratic senator's request for notes of his call with Mueller.

"Did you or anyone on your staff memorialize your conversation with Mueller?" Blumenthal of Connecticut asked.

Barr said a staffer took notes on it.

"May we have these notes?" Blumenthal asked.

"No,” Barr replied, adding, “why should you have them?"

Several 2020 Democratic presidential candidates – California Sen. Kamala Harris, New Jersey Sen. Cory Booker and Minnesota Sen. Amy Klobuchar – were among those who questioned Barr. Harris, after questioning the attorney general, used her campaign Twitter account to call for Barr’s resignation -- something other Democratic hopefuls also did Wednesday.

In another dramatic moment, Missouri Republican Sen. Josh Hawley lambasted the anti-Trump text messages between former FBI employees Lisa Page and Peter Strzok, telling Barr, "That's why we're sitting here today. An unelected official in this government has open disdain for Trump voters then try to overturn the results of a Democratic election. That's the story here today.”

Hawley added, “I can't believe a top official would try to exercise their own prejudices. That's the real crisis here."

Barr, meanwhile, told the panel he’s actively looking into the origins of the Russia probe, saying he’s working with FBI Director Chris Wray “to reconstruct what went down.”

Earlier, Barr testified that he was surprised Mueller didn’t come to a conclusion over whether Trump obstructed justice.

“We did not understand exactly why the special counsel was not reaching a decision,” Barr told the Senate Judiciary Committee.

Barr also defended his decision to release a summary of Mueller’s findings initially, before later releasing a redacted version of the report. He suggested the full report would have been released sooner, if Mueller’s team had cooperated with their request to identify sensitive grand jury material from the start.