Hillary Clinton has made the needs of families with young children central to her presidential campaign, citing de Blasio’s Pre-K For All as a model initiative. Nationally, somewhere between a third and half of American 4-year-olds are not enrolled in preschool, and polls show 70 percent of Americans would support the federal government making a large investment in early education. De Blasio’s Pre-K For All is the biggest and boldest recent model for how to do that. And yet, some policy experts believe it isn’t the right one.

By the time I was summoned into the mayor’s office to talk about pre-k, he was smiling broadly. He is famously tall: 6’5”. When you sit down with him, he hunches over, folding himself into a size that resembles your own. “I'm in pleasant shock that we got this far and this effectively,” he said. He spoke persuasively about Pre-K For All’s play-based pedagogy, “helping kids learn their numbers, working on their phonics, and learning their letters … I think there's an assumption that a rigorous curriculum somehow comes with draconian measures in the classroom,” he continued. “[Our classrooms] are filled with play and creativity and art and music. They're very uplifting. They're very open. There's lots of choice for kids.”

In 2016 there is one central debate, between the left and center-left, about the role of government in America. Can the widening gap in opportunity and life outcomes between the rich and the poor be closed using the dominant policy tools of the last 30 years: tax credits that are supposed to encourage minimum-wage work, and stigmatized, underfunded social programs that serve only the poorest of the poor, like Medicaid, food stamps, and Head Start, the federal preschool program? Or, does the country need to return to an older, and until very recently, largely unpopular idea: taxing the rich to create big, new government entitlements, like pre-k, free college, or single-payer health care—entitlements available to everyone, including the affluent who currently have little trouble procuring such services on the private market?

This was the crux of the debate between Bernie Sanders and Hillary Clinton. The signature Sanders policy proposal was a plan to make public college free for all. Even for the children of Donald Trump, as Clinton pointed out in one primary debate. Clinton became the Democratic Party standard-bearer, and after negotiations with Sanders, announced her own plan to make in-state public college free, but only for families earning under $125,000 per year.

There are few places in the United States to look for big, new experiments in universal government entitlements. One of them is New York City under de Blasio. The mayor issued a late-in-the-game primary endorsement of Clinton—he was the manager of her 2000 Senate campaign—but his Pre-K For All program is, notably, in the Sanders style: unabashedly free-for-all. Some American social programs, like Medicare and Social Security, serve everyone, and have proven to be relatively popular and politically sacrosanct. Others, like Medicaid, Head Start, food stamps, and cash welfare, are available only to the destitute, and are under constant threat of budget cuts. Pre-K For All is for the poor, the rich, and everyone in between. The mayor would rather speak about the program’s educational quality than its political strategy, but if prodded, will concede, “anything that has a broad constituency will also have more sustainability.” Simply put, it is difficult for politicians to retract a benefit that the politically powerful upper-middle class enjoys.