Sen. Elizabeth Warren has teamed up with three other senators to introduce legislation that would revive the Depression-era Glass-Steagall separation of investment and commercial banks, effectively breaking up the biggest Wall Street banks.

The legislation, which was also submitted in the last Congress, is not likely to advance in the current political environment. But it serves as a marker of the kind of change in finance that the populist Massachusetts Democrat has pushed for.

Glass-Steagall also could factor into the Democratic presidential primary. Two candidates for the nomination, former Maryland Gov. Martin O'Malley and Vermont Sen. Bernie Sanders, have endorsed reinstating it.

"Despite the progress we've made since 2008, the biggest banks continue to threaten our economy," Warren said in introducing the bill. "The biggest banks are collectively much larger than they were before the crisis, and they continue to engage in dangerous practices that could once again crash our economy."

Joining Warren in sponsoring the bill, called the 21st Century Glass-Steagall Act, are Sens. John McCain, R-Ariz., Maria Cantwell, D-Wash., and Angus King, I-Maine.

Glass-Steagall became law in 1933, but its main provisions were repealed in the 1999 Gramm-Leach-Bliley Act.

The main effect of the new bill would be to prevent banks that take deposits and receive deposit insurance backed by taxpayers from engaging in investment banking, offering insurance or engaging in derivatives transactions.

Speaking on the Senate floor Tuesday afternoon, Warren said that the legislation by itself would not solve the problem of banks becoming "too big to fail" and getting government bailouts in an emergency.

She claimed, however, that it would make the financial system safer by preventing bankers from trying to make speculative bets with deposits insured by taxpayers, and force them to take greater responsibility for their own investments. "It will stop the games that these banks have played for far too long," she said.

Tony Fratto, partner at the policy and communications firm Hamilton Place Strategies that represents some large financial firms, dismissed the new bill.

"This exercise is as irrelevant as it was last time," Fratto said. "It went nowhere before and it's going nowhere again. It's hard to take seriously a proposal that Senator Warren herself concedes would not have prevented the crisis."