Milei's Win in Argentina Sealed by a Risky Gamble That Turned Rival Into Ally

It was early in the afternoon of Oct. 22, the day of Argentina’s first-round vote, and Patricia Bullrich already knew that she’d lost her bid for the presidency. Eliminated from the runoff, Bullrich, the pro-business candidate for the main opposition Juntos por el Cambio bloc, couldn’t sleep that night. At 4 a.m. she sent a message to Mauricio Macri, the bloc’s elder statesman, saying that she wanted to back outsider Javier Milei, according to a person familiar with her movements. Bullrich, who earned a reputation for toughness during her time...