Elizabeth Warren is cast as many things: a populist, a left-winger, the paladin against the bankers and the rich, the Democrats’ alternative to Hillary Clinton, the policy wonk with a heart.

The senior senator from Massachusetts is certainly a populist and her heart is with those foreclosed upon and exploited by shady financial practices. But she is not nearly as left-wing as many say — she can offer a strong defense of capitalism that’s usually overlooked. And here’s betting that she won’t run against Clinton.

What all the descriptions miss is Warren’s most important contribution to the progressive cause. She is, above all, a lawyer who knows how to make arguments. From the time she first came to public attention, Warren has been challenging conservative presumptions embedded so deeply in our discourse that we barely notice them. Where others equivocate, she fights back with common sense.

Since the Reagan era, Democrats have been so determined to show how pro-market and pro-business they are that they’ve shied away from pointing out that markets could not exist without government, that the well-off depend on the state to keep their wealth secure and that participants in the economy rely on government to keep the marketplace on the level and to temper the business cycle’s gyrations.

Warren doesn’t back away from any of these facts. In her new book, “A Fighting Chance,” she recalls the answer she gave to a voter during a living-room gathering in Andover, Mass., that quickly went viral. She was in the early days of her Senate campaign, in the fall of 2011, and had been asked about the deficit. Characteristically, she pushed the boundaries beyond a narrow fiscal discussion to explain how government helped create wealth.

“There is nobody in this country who got rich on his own,” she said. “Nobody. You built a factory out there? Good for you. But I want to be clear: You moved your goods to market on the roads the rest of us paid for. You hired workers the rest of us paid to educate. You were safe in your factory because of police forces and fire forces that the rest of us paid for.” It was all part of “the underlying social contract,” she said, a phrase politicians don’t typically use.

Warren’s book tells her personal story in a folksy way and documents her major public battles, including her successful effort to establish a Consumer Financial Protection Bureau. But the book is most striking for the way in which her confident tone parallels Ronald Reagan’s upbeat proclamations on behalf of his own creed. Conservatives loved the Gipper for using straightforward and understandable arguments to make the case for less government. Warren turns the master’s method against the ideology he rhapsodized. Even former treasury secretary Timothy Geithner, who tangled with Warren, acknowledges in his new book “Stress Test” that she has “a gift for explanation.”

Warren tells of meeting with Rep. Michael Grimm (R-N.Y.), a former FBI agent, to talk about the consumer agency. “After a bit,” she reports, “he cut me off so he could make one thing clear: He didn’t believe in government.”

That seemed strange coming from the graduate of a public university and a veteran of both the military and a government agency, though Warren didn’t press him then. “But someday I hoped to get a chance to ask him: Would you rather fly an airplane without the Federal Aviation Administration checking air traffic control? Would you rather swallow a pill without the Food and Drug Administration testing drug safety? Would you rather defend our nation without a military and fight our fires without our firefighters?”

How often are our anti-government warriors asked such basic questions?

But doesn’t being pro-government mean you’re anti-business? Well, no, Warren says, quite the opposite. “There’s nothing pro-business about crumbling roads and bridges or a power grid that can’t keep up,” she writes. “There’s nothing pro-business about cutting back on scientific research at a time when our businesses need innovation more than ever. There’s nothing pro-business about chopping education opportunities when workers need better training.”

Oh yes, and it really bugs her when people assert that “corporate” and “labor” are “somehow two sides of the same coin.” She asks: “Does anyone think that for every billionaire executive who can afford to write a check for $10 million to get his candidate elected to office, there is a union guy who can do the same? Give me a break.”

At the end of a long liberal era, Reagan electrified conservatives by telling them they didn’t have to apologize anymore for what they believed. Now, Warren insists, it’s the era of liberal apologies that’s over.

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