Noting that he’s long supported reimposing a firewall between investment and commercial banks, the Vermont senator said he’s officially rejoining an effort led by Sens. Elizabeth Warren (D-Mass.) and John McCain (R-Ariz.) to break up the big banks, saying, “If we are truly serious about ending too big to fail, we have got to break up the largest financial institutions in this country.”

“Allowing commercial banks to merge with investment banks and insurance companies in 1999 was a huge mistake. It precipitated the largest taxpayer bailout in the history of the world. It caused millions of Americans to lose their jobs, homes, life savings and ability to send their kids to college,” said Sanders, who said that change in the financial world “substantially increased wealth and income inequality.”

Earlier this week, a Clinton campaign adviser toldReuters that “you’re not going to see Glass-Steagall.” Clinton was also interruptedby a heckler on Monday who challenged her to revive the depression-era policy, though she did not answer the question.

By moving quickly to reassert his support for a proposal from liberal superstar Warren, Sanders is highlighting the differences between his platform and Clinton’s more centrist positions on financial regulations, a major issue among progressives. Sanders actually cosponsored a version of the bill in 2013, well before he began challenging Clinton for the Democratic nomination, and in a press release reminded reporters of a speech he gave in 1999 as a House member.

“Sixteen years ago, I predicted that such a massive deregulation of the financial services industry would seriously harm the economy. I would give anything to have been proven wrong about this, but unfortunately, what happened seven years ago was even worse than I predicted,” Sanders said.

In 1999, Congress passed legislation rewriting the financial rule book for banks, and it was signedby President Bill Clinton.