Tensions flared up between Hillary Clinton and Sen. Bernie Sanders during Thursday night’s Democratic debate, as the candidate sparred about whether Clinton espouses progressive politics.

A question about why liberal Democrats should back Clinton over Sanders resurrected a Wednesday dustup between the candidates after Sanders said of Clinton: “You can be a moderate. You can be a progressive. But you cannot be a moderate and a progressive.”

“I am a progressive who gets things done,” Clinton answered. “The root of that word, progressive, is progress.”

She continued: “I’ve heard Sen. Sanders’ comments. It’s really caused me to wonder who’s left in the progressive wing of the Democratic party. Under his definition, President Obama is not progressive because he took donations from Wall Street. Vice President Biden is not progressive because she supported Keystone.”

Clinton said if Sanders wants “to get into labels,” Sanders’ record is less than sterling, and criticized the senator for his vote to give gun makers and sellers immunity, voting against Sen. Ted Kennedy’s immigration reform, and multiple votes against the Brady bill.

In his response, Sanders said voters need to “wage a political revolution” and said his policy ideas “are not radical ideas.”

But MSNBC’s Chuck Todd didn’t let Sanders off the hook, and asked if he considered Obama a progressive by his definition.

Sanders responded that he was simply using Clinton’s own words, saying the former secretary of state has previously called herself a “moderate.”

“There’s nothing wrong with being a moderate, but you can’t be a progressive,” he said. “Do I think Obama is a progressive? Yeah, I do.”

Clinton responded that “cherry picking” quotes doesn’t change her record, and said the smear was part of Sanders’ campaign to “distinguish himself” as a “self-proclaimed gatekeeper for progressivism.”

“I don’t know anyone else who fits that definition,” she said. “I know a lot of really hard fighting progressives in the Democratic party who have stoods up time and time again against special interests and the powerful against those who have been left behind and left out.”