Every day now, it seems, another Democratic candidate announces his or her 2020 presidential run. Among the most popular ideas these hopefuls campaign for is a tuition-free higher education. “A free-college proposal has practically become an entrance fee,” says writer Adam Harris.

In a new Atlantic Argument, Harris explains that while this is an intriguing idea, it is also a vague and sweeping one, and voters want policy specifics. “The nuts and bolts of education proposals in the 2020 election,” Harris says, “are critical to understanding whether or not, six years from now, the student-debt bubble reaches $2.5 trillion, or even $3 trillion.”