Gretchen Ertl / Reuters

For the fourth time in three presidential debates, Senator Elizabeth Warren of Massachusetts in Houston on Thursday faced a variation of the same question from a moderator: Will she raise taxes on the middle class to fund Medicare for All?

And for the fourth time, Warren deployed what in politics is known as an artful dodge. She didn’t say yes, and she didn’t say no. “Those at the very top, the richest individuals and the biggest corporations, are going to pay more,” she told the moderator George Stephanopoulos. “And middle-class families are going to pay less. That’s how this is going to work.”

Stephanopoulos dutifully followed up: “Direct question,” he said. “You said middle-class families are going to pay less. Will middle-class taxes go up to pay for the program?”

Again, Warren deflected. “What families have to deal with is cost, total cost. That’s what they have to deal with,” she replied. “What we’re talking about here is what’s going to happen in families’ pockets, what’s going to happen in their budgets. And the answer is Medicare for All. Costs are going to go up for wealthier individuals, and costs are going to go up for giant corporations. But for hard-working families across this country, costs are going to go down, and that’s how it should work under Medicare for All in our health-care system.”

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.

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.

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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