Why did Peña Nieto invite Trump to Mexico?

Donald Trump will clarify his immigration policies in a speech in Arizona Wednesday; but first, he’ll make a pit stop in Mexico City to meet privately with Mexico’s President Enrique Peña Nieto. The Republican presidential candidate is very unpopular in Mexico; but so is Peña Nieto, whose approval rating hit a record low of 23 percent this month. Peña Nieto once compared Trump to Hitler, so why would he welcome him to Mexico now?