The repeal of the Glass-Steagall act in 1999 directly caused the 2007 Financial Crisis and the resulting depression that the nation has only begun to rise out of in recent years.
The removal of regulations preventing banks from combining commercial and investment banking led to commercial and investment banks being able to merge. Many had already begun the process, including J.P. Morgan and Citicorp. The updated ground rules were low on oversight and heavy on risky ventures.
This led to predatory lending, trading of mortgage-backed securities, and dozens of other dishonest practices that caused the recession. By endorsing the reinstatement of the glass-steagall act, the president could make the most significant move in the the last decade to protect citizens and the economy from banks