Shannon Stapleton / Reuters

Joe Biden and Elizabeth Warren both want to be the 2020 Democratic nominee. But first, they want some credit.

The top rivals in this year’s primary got into their most prickly exchange of the race yet at tonight’s debate in Ohio, bickering over who was most responsible for a key element of former President Barack Obama’s domestic legacy: the creation of the Consumer Financial Protection Bureau.

The fight started when the former vice president pitched himself as the most experienced and effective candidate on the stage. “I’m going to say something that is probably going to offend some people here, but I’m the only one on this stage that has gotten anything really big done,” Biden said.

It was an audacious claim that referenced Biden’s reputation as a dealmaker over his decades in the Senate, but it opened the door for Warren to tout her widely acknowledged role in the consumer agency at the heart of the 2010 Wall Street reform bill. Then a Harvard professor, Warren became the bureau’s public face and stood it up once Congress enacted the law; she wasn’t named to be its first director largely because Republicans vowed to block her confirmation in the Senate.

Yet when Warren pointed all this out tonight, Biden replied angrily. “I agree with the great job she did, and I went on the floor and got you votes,” he said, his voice rising as he pointed his hand directly at Warren. “I got votes for that bill. I convinced people to vote for it, so let’s get those things straight, too.”

Warren responded by ignoring Biden’s role entirely. “I am deeply grateful to President Obama,” she said, speaking slowly and deliberately, “who fought so hard to make sure that agency was passed into law, and I am deeply grateful to every single person who fought for it and who helped pass it into law.”

“You did a hell of a job in your job,”  Biden shot back.

Warren went on to point out that Obama “sometimes had to fight against people in his own administration.”

“Not me,” his former vice president interjected.

Democratic primary voters probably don’t care much who deserves more credit for the Consumer Financial Protection Bureau. But the exchange between Biden and Warren wasn’t a scrape over ideology so much as it underscored the difference between the two rivals over their approach to governing.

For Biden, the test of success is measured in votes won, colleagues persuaded, deals struck. Warren sees victory in the broader fight for support, in the groundswell among the grassroots that causes legislators to act, and to act boldly. “Understand this: It was dream big, fight hard,” she said. “People told me, ‘Go for something little. Go for something small.’”

The implication was that while Biden champions compromise, the creation of the consumer agency was an example of the “structural change” around which Warren has centered her campaign. As the newly anointed front-runner in the race, it seems more and more Democratic voters are embracing Warren’s vision.

But as Biden and Warren separate themselves from the primary field, their debate over the right kind of experience and the size and scope of the party’s ambition is likely just beginning.

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