There is a simple metric that many will use to judge the performance of Guatemala’s next president: Can he stop the exodus of people fleeing the country? Alejandro Giammattei, the leader of the right-wing Vamos party who won Sunday’s runoff convincingly over Sandra Torres of the center-left National Unity of Hope party, says he has a plan. But there are many reasons to be skeptical.

According to local estimates, nearly 250,000 Guatemalans left their country in the first half of this year, equivalent to 1.5 percent of the population of some 17 million, and most of them headed for the United States. Data from U.S. Customs and Border Protection shows that Guatemalans are the largest nationality among migrants from the three countries of Central America’s Northern Triangle region entering the U.S. In an attempt to stem that flow, the Trump administration recently signed a “safe third country” agreement with Guatemala’s outgoing president, Jimmy Morales, which would require asylum-seekers from other countries transiting Guatemala to seek asylum there first. ...