MEXICO CITY—Former first lady Margarita Zavala said she is withdrawing her candidacy for the July 1 presidential election, likely giving a boost to Ricardo Anaya of the conservative National Action Party, who polls say is in second place, ahead of a Sunday debate.
Wednesday’s announcement, which narrowed the field to four, was followed by gains in the peso against the dollar. Ms. Zavala’s withdrawal could narrow the double-digit poll lead of leftist nationalistAndrés Manuel López Obrador, who is widely seen as the least market-friendly...