Public support for charter schools has declined substantially in the last year, according to a national survey released Tuesday.

The survey, conducted by the school choice-friendly journal Education Next, found that slightly more Americans support charter schools, 39 percent, than oppose them, at 36 percent. But that marks a drop from 51 percent support just last year — one of the biggest changes in public opinion seen in the long-running survey, according to Harvard professor and the magazine’s editor-in-chief Marty West.

“The sharp drop in support for charter schools constitutes the major change in the school-choice battle over the course of the past year,” wrote West and others in an accompanying essay.  

Results from the annual survey, which polls a representative sample of American adults, come as charter schools have faced a number of recent setbacks.

The NAACP and National Education Association both recently codified positions designed to restrict the growth of charter schools. Last year, charter advocates suffered a high-profile defeat at the ballot box in Massachusetts, where voters overwhelmingly rejected a ballot measure to lift the state cap on charter schools.

At the same time, Donald Trump, a charter school backer, was elected president, and his Secretary of Education Betsy DeVos has also been a strong supporter of the publicly funded but privately managed schools.

“The opinions about charter schools that matter most are the opinions of parents and students who have chosen charter schools,” said Nina Rees, the president of the National Alliance for Public Charter Schools, in a statement. “This dip in broad public approval, as reported by Education Next, seems more reflective of the unique moment we’re in.”

But the poll finds little evidence that the fall in charter school support is related to Trump or DeVos.

For one thing, backing for private school choice programs — like vouchers or tax credit programs — generally held steady, even though the Trump administration has also praised that approach. Moreover, support for charter schools declined substantially this year among both Democrats and Republicans.

The survey also also informed one group of respondents that Trump supports charter schools and then asked their opinion; another set of people were not told Trump’s position.

Knowing Trump’s views actually led to a net increase in support for charters, with large bumps for Republicans and essentially no effect among Democrats.

It’s unclear, then, what accounts for the drop in support for charter schools. West suggested that increasingly pitched locally debates, like those in Massachusetts and elsewhere, may be part of the explanation.

And while charter school supporters might at least hope that support for charters is higher in states with a lot of them — the idea being that once voters get to know charters, they like them — there is no evidence for that, either.

In an analysis shared with Chalkbeat, West found no correlation between how many students attended a charter in a given state and support for charter schools. That mirrors the election results within Massachusetts, where the ballot initiative to lift the cap on charters lost across the state — even in cities like Boston, where many students attend charter schools.