But last week’s debates were less successful in clarifying how the Democrats differ on immigration. To be sure, the candidates offered policy proposals: They called for restoring DACA, reforming Immigration and Customs Enforcement, eliminating private detention centers, and giving undocumented immigrants health care and a path to citizenship. In the first debate, Julián Castro also declared his support for downgrading illegally crossing the border from a criminal to a civil offense, and then slammed Beto O’Rourke for disagreeing with him. But while O’Rourke has in the past argued against decriminalization, he wouldn’t defend that position onstage, and instead said he opposed criminalizing asylum seekers, thus evading Castro’s broader point. He was willing to play the centrist on health care, just not on immigration.

In the second debate, the moderator José Diaz-Balart asked for a show of hands on decriminalization. Eight candidates raised their hands; Biden—oddly—raised a finger. But the moderators didn’t ask him to explain. So while viewers were left with a sense that the presidential candidates have different views on decriminalization, they learned nothing about why.

Even more important, the candidates didn’t define the criteria that should govern who gets asylum. That’s significant, because over the past few years, the kinds of people crossing America’s southern border without immigration papers have radically changed. A decade ago, the undocumented were mostly single Mexicans trying to evade capture. Now they’re mostly Central Americans who turn themselves over to Border Patrol so they can apply for asylum. This shift has overwhelmed the asylum process. Cases now regularly take five years to be resolved.

At the debates, Democrats bellowed their opposition to Trump’s handling of the asylum crisis. And they rightly emphasized the need to help Honduras, Guatemala, and El Salvador battle crime, corruption, and poverty so that fewer of their citizens make the perilous journey north. Although they didn’t say so at the debates, the three candidates who have issued immigration plans—Castro, O’Rourke, and Jay Inslee—have also proposed pouring money into the asylum system so asylum seekers can get lawyers and interpreters, and a faster resolution of their claims.

This all makes sense. But it also raises an uncomfortable question. As Bloomberg’s James Gibney has noted, one of the internationally accepted legal criteria for who deserves asylum—fear based on “membership of a particular social group”—is extremely vague. Different immigration judges interpret it in vastly different ways. Since those judges currently work for the attorney general, and thus ultimately for the president, the Democratic candidates need to clarify what standard they support. The easier they make it for asylum seekers to qualify—and the more successful they are in making the process faster and fairer—the more asylum seekers are likely to come. Eventually, improving conditions in Central America may stem the flow. But as Fareed Zakaria has pointed out, the number of asylum seekers from Honduras, Guatemala, and El Salvador has risen in recent years even as murder rates in those countries have dropped.