My plan also goes beyond the biggest banks to include the whole financial sector. Some have urged the return of a Depression-era rule called Glass-Steagall, which separated traditional banking from investment banking. But many of the firms that contributed to the crash in 2008, like A.I.G. and Lehman Brothers, weren’t traditional banks, so Glass-Steagall wouldn’t have limited their reckless behavior. Nor would restoring Glass-Steagall help contain other parts of the “shadow banking” sector, including certain activities of hedge funds, investment banks and other non-bank institutions. My plan would strengthen oversight of these activities, too — increasing leverage and liquidity requirements for broker-dealers and imposing strict margin requirements on the kinds of short-term borrowing that also played a major role in spurring the financial crisis. We need to tackle excessive risk wherever it lurks, not just in the banks.

Second, I would appoint tough, independent regulators and ensure that both the Securities and Exchange Commission and the Commodity Futures Trading Commission are independently funded — as other critical regulators are now — so that they can do their jobs without political interference. I would seek to impose a tax on harmful high-frequency trading, which makes markets less stable and less fair. And we need to reform stock market rules to ensure equal access to information, increase transparency and minimize conflicts of interest.

Finally, executives need to be held more accountable. No one should be too big to jail. I would seek to extend the statute of limitations for major financial crimes to 10 years from five and enhance rewards for whistle-blowers. I would work to ensure that financial firms admit wrongdoing as part of settlements in instances of egregious misconduct, and increase transparency about the terms of settlement and the fines actually paid to the government. Fines should be more than just the cost of doing business to these companies — they should be an effective disincentive for illegal behavior.

And it shouldn’t just be shareholders and taxpayers who feel the pain when banks make bad decisions; executives should have skin in the game. When a firm pays a fine, I would make sure that the penalty cuts into executives’ bonuses, too. And I would fight to close the carried interest loophole that gives some fund managers billions of dollars in tax breaks: They should be taxed like every other citizen.

Republicans may have decided to forget about the financial crisis that caused so much devastation — but I haven’t. The proper role of Wall Street is to help Main Street grow and prosper. When our financial sector works the right way, it helps families buy their first homes, entrepreneurs start and grow small businesses and hardworking Americans save for retirement. Rather than pursuing the kind of high-stakes speculation that devastated our economy before, Wall Street should focus on building an economy that creates good-paying jobs, rising incomes and sound investments so that more families can achieve the security of a middle-class life.