BUENOS AIRES (Reuters) - Daniel Scioli, the leftist frontrunner in Argentina's presidential election, widened his lead over his more business-friendly rival, but not enough to avoid a runoff, the first poll since Aug. 9 primaries showed on Sunday.
Scioli, who is a member of President Cristina Fernandez's Front for Victory party but supports a more pro-market approach to policy, and his candidate for vice-president, Carlos Zannini, are favored by 39.3 percent of voters ahead of the Oct. 25 ballot.
Mauricio Macri, the Buenos Aires mayor who espouses more orthodox economic policies, and his choice for running mate, Gabriela Michetti, have 31.2 percent.
Those results would still lead to a run-off election in November because to win outright in October, a candidate needs 45 percent of the vote or 40 percent with a 10-point margin over whoever places second.
The August poll by consultancy Management & Fit shows front-runner Scioli's lead growing from the 35.5 percent of support he obtained the prior month, while Macri, of the Cambiemos, or "Let's Change," coalition, saw his figures virtually unchanged from July.
In third place, dissident Peronist Sergio Massa and vice-presidential choice Gustavo Saenz were favored by 18.3 percent of voters.
Scioli came out on top of Argentina's presidential primary earlier this month, as voters approved the Buenos Aires governor's policy of gradual change after eight years of Fernandez's leftist government.
Each party chose its presidential candidate in the primary but with voters free to cross party lines, the primary vote served as a dry run ahead of the October election.
The pollster surveyed 2,400 people between August 20 and 26. The poll has an error margin of plus or minus two percentage points.
Reporting by Juliana Castilla; Writing by Anthony Esposito; Editing by Clelia Oziel