Former Sen. Jeff Flake, R-Ariz., defended his decision to publicly endorse Democratic candidate Joe Biden for president on "The Story" Monday, prompting host Martha MacCallum to ask Flake to name an "actual policy" of Biden's that he supports.

At one point, MacCallum asked Flake how, as a lifelong Republican, he is supporting a candidate who has promised to be "the most progressive president in history."

"I think, if you look at Joe Biden's record, he's not been that," Flake responded. "This is a primary that he has just been through. He also said he would work with Republicans ... that's not a popular thing to say in the Democratic primary, but he did.

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"He's a creature of the Senate," Flake added. "He knows how to compromise. He knows how to work across the aisle and I'm confident he will do that in the future."

MacCallum noted that Flake supported the First Step Act, a landmark bill signed into law by Trump that directs the Justice Department to create a system assessing the chances an inmate will offend again, as well create housing or other incentives for offenders to participate in recidivism reduction programs. Trump has described the bill as an effort to reform "sentencing laws that have wrongly and disproportionately harmed the African-American community."

"The president was actually able to sign that into law," MacCallum said. "We had eight years of the Obama-Biden administration and they did not take action on that. So why support Joe Biden over President Trump?"

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"I voted for that while I was in the Senate," Flake responded. "Joe Biden has been supportive of criminal justice reform ...

"We passed the bipartisan immigration bill that appropriated $20 billion for border security. That was when President Obama and Joe Biden were in the White House. We did that in the Senate. I've been supportive of many of the things that the president has pushed," he said.

"But you just dont like his character," MacCallum responded.

"It's not just that," Flake posited. "Republicans have traditionally been for free trade. The president is very much a protectionist. The Republicans have stood for strong American leadership ... He canceled the Trans-Pacific Partnership. The Trans-Pacific Partnership, if anything, would have helped keep China in check by allowing countries, particularly in southeast Asia, to go somewhere else for their trade."

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When MacCallum noted that Flake is pro-school-choice, while Biden has come out against for-profit charter schools, the former senior suggested that Biden will at least "stand up and have reverence for our institutions."

"There's something to be said for that," Flake added. "I think he will preserve the public space so that we can go back to disagreeing about policy and not just this tribalism that we see today."