UNITED NATIONS, July 25 — Four women and two men are in the running to succeed Antonio Guterres as leader of the United Nations, which faces unprecedented global instability, wars and its own crushing budget crisis.Observers say it is difficult to pick a favourite, given that the world’s major powers are divided on the outcome, but Argentina’s Rafael Grossi — the current head of the UN nuclear watchdog — has been repeatedly mentioned.Grossi is a candidate along with Chile’s Michelle Bachelet, Ecuador’s Maria Fernanda Espinosa, Costa Rica’s Rebeca Grynspan, Guyana’s Carolyn Rodrigues-Birkett and Senegal’s Macky Sall.Even if one candidate gets...