Conservative opposition candidate Mauricio Macri stunned Argentina's ruling party with an unexpectedly strong showing in the presidential election on Sunday, forcing a runoff vote next month, preliminary results showed.
Daniel Scioli, backed by outgoing leftist president Cristina Fernandez and her Front for Victory party, had a big lead in pre-election opinion polls and he had hoped for an outright victory on Sunday.
But the results showed the two men running neck-and-neck. With returns in from 86 percent of polling stations,Scioli had 35.9 percent support while Macri had 35.2 percent.
"What happened today will change politics in this country," Macri, the pro-business mayor of Buenos Aires, said in a speech to supporters.