MEXICO CITY—Mexicans voted Sunday on whether their president should end his six-year term barely midway through or continue to the end. Strangely, President Andrés Manuel López Obrador was the one who pushed for the first-ever referendum of its kind in Mexico. It was considered a safe bet. The referendum is only binding if at least 40 percent of the country’s electorate votes—something experts believe unlikely—and López Obrador has maintained approval ratings around 60 percent. With that in mind critics have decried the exercise as a waste of money—almost $80 million—and just a way for López Obrador to rally his base midway through his time in office. López Obrador voted early Sunday in downtown Mexico City, urging others to vote. “There always has to be democracy in the family, in school, in work, in the unions, of course in public life and you have to participate,” the president said. Some in …