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Before he was a multimillionaire, self-made investor, and entrepreneur, Sanberg, 39, grew up in Orange County, California, near Disneyland, as one of two sons of a single mother who did substitute teaching and editing, but was forever behind on bills. He learned young to hate the people who said hard work was all it took to get ahead.

Sanberg was a scholarship kid at a prep school who got into Harvard and went for a career on Wall Street that would pay him the most money right out of school. After the better part of a decade at Blackstone, he quit, made his way back to California, and hit it big as the founding investor in Blue Apron, the online meal-delivery company. He then became the founding shareholder in Aspiration, a financial-services company that specializes in socially conscious investments.

“Coming from poverty and at the same time being able to create wealth—he understands how they’re interconnected personally,” said Representative Ruben Gallego of Arizona, a close friend who bonded with Sanberg at Harvard, where they were poor kids amid a sea of classmates with yachts and their names on buildings. “A lot of these politicians are talking on a theoretical level.”

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For the past five years, Sanberg has been funding a nonprofit he created called Working Hero, which has helped 2 million low-income people a year get more cash back on their federal income. After creating the nonprofit, he founded the Working Hero PAC, which lobbies and backs candidates who support anti-poverty efforts.

This year, to deliberately inject Working Hero’s tax-counseling services into the presidential race, he opened chapters in Iowa and South Carolina. Following up on the event he did with Booker, Elizabeth Warren will appear at a Working Hero event during her swing through Iowa this weekend.

Even though Republicans under Donald Trump seem to have abandoned their traditional objections to deficit spending and government intervention in corporate affairs, Sanberg believes Democrats are still largely allowing the GOP to set the terms of the economic debate and frame it as a clash between the conservative party of small government and growth, and the socialist party of big government and welfare.

For all the economic ideas from the left that have become early litmus tests in the Democratic primary race, the only real argument for growth is coming from Washington Governor Jay Inslee and his pitch that renewable energy and environmental cleanup are job creators. He talks about raising the minimum wage in Washington and having the most robust state economy in the country.

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Sanberg thinks only a successful entrepreneur who’s also a progressive can make those arguments on a broader scale with any success. He thinks increasing the minimum wage will do more than corporate tax breaks to stimulate the economy. “I’m so sick and tired of Republicans calling us socialists,” Sanberg said at the event with Booker, at which his nonprofit worked to help people file tax returns and receive the $3,000 they’re eligible for under the earned-income tax credit. “The true socialists are Republicans, because they have socialism for monopolies, and then competition for the rest of us, fighting like crabs in a bucket over scraps.”