On this point, a look back at the most successful Democratic administration in American history—Franklin D. Roosevelt’s New Deal—is illustrative.

Taking power three years into the Great Depression, the Roosevelt administration famously wrought fundamental changes to American political, economic, and social life. Yet that only happened because Roosevelt and others first convinced the country that fundamental changes were desperately needed. As historian Eric Rauchway has recently reminded us, FDR spent the 1932 campaign making the case for a drastic new direction. But Roosevelt wasn’t alone.

That same year, the Senate held hearings to uncover the causes of the crash. After 10 months, though, the Committee on Banking and Currency had accomplished little. Two successive investigators were dismissed for lackluster work, and a lack of results, before a third one was hired in January 1933, with hopes he might be able to scrounge some sort of report out of the thin findings and help the Senate save face.

The new investigator, Ferdinand Pecora, seemed an unlikely choice for Washington. A Sicilian immigrant from the East Side of New York City, Pecora had worked his way up through the District Attorney’s office handling major cases against murderers, gangsters, racketeers, and corrupt politicians. He sent the state Banking Commissioner to Sing Sing and nearly put a State Comptroller there too. Pecora also turned his attention to Wall Street, closing down 150 “bucket shops”—shady outlets that handled illegal bets on stock performances—and sending several of their owners to jail.