For Democratic candidates now, the question is not so much whether to support a plan to make college more affordable, but what the right approach is for doing so. The details—whether there is an income cap for eligibility; whether the government covers tuition costs up front before grants; whether there are merit or GPA requirements—will determine who will benefit the most, and who will pay for such a plan.

A subtle tweak from Kamala Harris this past January encapsulates the coming debate over the scope of the party’s proposals. The senator from California, while making formal what many had suspected—that she would be running for president—tweaked her language in a slight but potentially significant way. She was supporting free college, but not just any free college: She was pushing for debt-free college. “I am running to declare education is a fundamental right,” she said, “and we will guarantee that right with universal pre-K and debt-free college.”

What was the difference? Free college is a catchall term for a range of college-affordability plans. There are “tuition-free” programs, where the government—or an institution—covers tuition but not the other expenses, such as books, housing, or food; then there are debt-free college plans, which aim to address all those other costs. Harris was getting specific; and she was doing so with the kind of free-college idea—debt-free—that equity advocates tend to prefer.

Oftentimes, tuition-free models are “last dollar,” which means that the government covers tuition after all other grant aid—such as Pell Grants, which are federal grants for low-income students—is applied. Oftentimes those grants cover the full tuition at community colleges, and students aren’t able to use that money for things like books, housing, or food. These are things that they may ultimately have to take on debt to afford. “Progressive candidates need to be talking about debt-free college instead of just free college, and going beyond tuition for low-income students,” Tiffany Jones, the director of higher-education policy at the Education Trust, an advocacy group for low-income students, told me.

Harris’s declaration was a departure from her language in 2016, when she first introduced a plan, toward the end of her Senate campaign, to make community college tuition-free for all, and four-year college tuition-free for families making less than $140,000 a year; it was even a departure from weeks prior, when she pushed for tuition-free college. Her development signaled, perhaps above all, how the Democratic Party has evolved on college affordability.

Read: Why is college in America so expensive?

The United States has a long history of college-access and -affordability policies—the first Morrill Act, the GI Bill, etc.—that did not provide equitable access or universal affordability, particularly for minorities. Advocates hope that a similar mistake won’t be made with a potential national free-college policy, and that debt-free college becomes the new gold standard.