David McNew/Getty Images Former Ohio state Sen. Nina Turner, seen here at a Sanders campaign town hall in Los Angeles in July, is one of his most combative surrogates.

DES MOINES, Iowa ― Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) discussed their disagreement about their private 2018 conversation on the electability of female candidates relatively amicably on the debate stage on Tuesday night.

But in a related exchange, Warren tripped Sanders up with her claim that she was the only person onstage to have unseated an incumbent Republican in the past 30 years. When Sanders later asked to “set the record straight” that he had unseated a Republican in 1990, Warren reminded him that that was 30 years ago (though it was actually just over 29 years ago).

Sanders campaign co-chair and former Ohio state Sen. Nina Turner expressed her dismay with Warren’s comments in a conversation with reporters after the debate.

Asked whether Warren’s 30-year comment was an unfair jab at Sanders, Turner replied, “You should ask [Sen. Warren] that, but I know 30 years ago she was a Republican.”

In the two days leading up to the debate, many progressive groups nervous about a spat between Sanders and Warren were urging them to bury their differences out of a shared commitment to blocking more centrist Democrats from nabbing the presidential nomination.

Turner suggested that if the debate had failed to ease tensions between the two candidates, a greater share of the blame lay with Warren.

“Sen. Sanders made a point that he beat a Republican. Just leave it at that,” she said. “Sen. Warren took it to a whole ’nother level. That was not necessary to do that.”

Warren was indeed a registered Republican until the mid-1990s. She said her research as a legal scholar into the root causes of household bankruptcy reshaped her worldview. As a Democrat, she defeated Republican Sen. Scott Brown in 2012 in her first run for office.

After Tuesday’s debate, a reporter asked whether the two senators’ failure to shake hands at the end meant that they continue to be at odds with one another.

“Go back and watch the clip. Sen. Sanders put his hand out,” Turner said. “You just shake your colleague’s hand, but again, we’re getting caught up on this.” (The video indeed shows Warren refusing Sanders’ hand.)

Adam Green, a co-chair of the Progressive Change Campaign Committee, which is backing Warren, took a more conciliatory approach, declining to disparage Sanders for his handling of the exchange.

“What we saw tonight was the escalation and then a quick pivot to offense and the most definitive electability case we’ve heard from Elizabeth Warren so far about how a woman can win,” Green said. “It was devastating.”

Turner, a veteran of the 2016 Sanders run and frequent surrogate for Sanders on the campaign trail, often relishes her role as an attack dog for the Vermont senator. She delivered the toughest hits against Sanders’ opponents in her remarks at Sanders’ post-heart attack comeback rally in New York City in October, and just this week, she wrote an op-ed in a South Carolina newspaper attacking former Vice President Joe Biden’s record on race.

But Turner has sometimes struggled to clarify whether her remarks represent the campaign’s official stance. When delivering a speech ahead of the November debate in Atlanta, she blasted former South Bend, Indiana, Mayor Pete Buttigieg and simultaneously insisted she was not speaking on the campaign’s behalf.

And her comments Tuesday night exposed Sanders to a line of criticism he has sought to avoid: his own refusal to formally affiliate with the Democratic Party.

“Desperation sure is cute,” Wesley Whistle, an expert at the New America Foundation supporting Warren, tweeted. “If only Bernie was EVER a Democrat.”