(CNN) Joe Biden is in -- and the knives are out.

Sen. Elizabeth Warren of Massachusetts welcomed the former vice president to the 2020 Democratic primary on Thursday by reminding voters of their old clashes over the nation's bankruptcy laws.

"I got in that fight because (families) just didn't have anyone and Joe Biden was on the side of the credit card companies," Warren said after being asked about the issue following a rally in Iowa. "It's all a matter of public record."

The nearly two-decade-old Warren-Biden feud is, indeed, well documented. Warren has, in multiple interviews and op-eds, criticized Biden, during his time in the Senate, over his role in moving along legislation she believed would benefit big banks at the expense of working and middle-class Americans.

Warren was joined by her Senate colleague Bernie Sanders in jabbing Biden, who is poised to head up the moderate Democratic opposition to President Donald Trump in a year when progressive primary candidates have been dominating the headlines. Both of the New England senators view Biden as an ideological foe that, despite his strong early polling, could ultimately provide a useful political foil. Sanders' campaign sent a pair of fundraising emails on Thursday, both with Biden's name in the subject line, pushing supporters to meet the challenge ahead.

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