The exchange was familiar, because Warren had answered a pair of similar questions in a similar way from CNN’s Jake Tapper at the last Democratic debate, in Detroit.

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The word taxes appeared nowhere in her answers, and that’s a clue that yes, taxes for the middle class may be going up under Warren’s plan, which she has adopted from Senator Bernie Sanders of Vermont. What she’s arguing is that any increase in taxes will be more than offset by the reduction in costs that people will have to pay for health care under a government-run system. Premiums will be much lower; deductibles will be much lower; the price of medication will be lower. So what, Warren is suggesting, if middle-class families have to pay a bit more up front if their overall financial burden is going down? But for now, she’s shying away from outlining the trade-off explicitly.

The distinction she is trying to make may seem wonky, but it goes to the heart of the risky politics that Democrats have long had to navigate in proposing major expansions to government services, and nowhere more so than in health care. Back in 1992, then–Arkansas Governor Bill Clinton told voters he would not raise taxes to pay for his programs, but he pointedly declined to repeat the infamous “Read my lips; no new taxes” pledge that President George H. W. Bush made four years earlier and later broke. Ultimately, Clinton did raise taxes on the middle class.

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Over the years since, Democratic presidential candidates from Barack Obama to Hillary Clinton have clung to an unspoken rule: Proposals to raise taxes on the rich are okay, but tax increases on the middle class are out—or at least not acknowledged.

Warren is running on bold ideas, and climbing in the polls as something of a truth teller. At the debate in Detroit, she railed against “small ideas and spinelessness,” and she implored her fellow Democrats not to be afraid of, or adopt, Republican attacks on Medicare for All. But she is facing competition from an even more candid rival in Sanders, who has said that middle-class taxes might have to rise to pay for truly universal health care.

Her reluctance to acknowledge as much is a sign both of her evolution as a politician and her standing in the Democratic race. Warren’s rising in the polls now, and she likely has at least one eye on the general election next year. And while she’s betting that the country is ready for a real debate on government-run health care, she’s sticking to her party’s age-old wariness of telling middle-class families in a simple sound bite that their tax bill might go up.

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