BUENOS AIRES, Sept 23 (Reuters) - Argentina's ruling party candidate in October's presidential election has eked out slim gains over his main rivals in the past month, putting him within striking distance of winning the first round and avoiding a run-off, opinion polls showed. Three polls in September put the Front for Victory's Daniel Scioli within 2 points of the 40 percent threshold for an outright win if he holds a 10 point margin over nearest rival Mauricio Macri, of the business-friendly PRO party. The polls showed Scioli jumping the 40 percent barrier if undecided voters are distributed among the candidates, though the polls' margin of error leaves the Oct. 25 vote on a knife edge. "A mere change of two or three points for either candidate can mean the difference between a first-round win or run-off," said Ignacio Labaqui of emerging markets consultancy Medley Global Advisors. Scioli had been expected to receive a stronger bounce after last month's party primaries but voter frustration at his handling of flooding in his home province and accusations of ballot burning in a provincial election won by the ruling party have checked his gains. Scioli has made new investment a cornerstone of his campaign platform, but has given few clues on the changes he would make to state controls on the economy imposed by outgoing President Cristina Fernandez, often defending her policies instead. Market-favorite Macri, who is campaigning on a platform to reduce the state's role in the economy and an end to the broad-based Peronist movement's domination of Argentine politics, has struggled to close the gap on Scioli. His promise to clean up Argentine politics has been dented by a corruption scandal involving a political ally, while diplomats privately say he struggles to connect with voters and lacks the hunger for the presidency that Scioli displays. That has given a fillip to third-placed Sergio Massa. If no candidate wins 45 percent of valid votes or achieves 40 percent with a 10 point margin, the election will go to a second round on Nov. 22. Analysts say a run-off could go either way. "He's got to focus on getting to the second round, it's all or nothing for Macri in the first round," said 45-year-old Juan Pablo Rivero, a supporter of the Buenos Aires mayor. The following are results from the latest polls. Numbers in brackets denote projected results when undecided voters are included. Scioli Macri Massa Management & Fit 36,7 pct 29,2 pct 17,1 pct (39,3 pct) (31,2 pct) (18,3 pct) CEOP Latam 39,0 pct 29,3 pct 15,6 pct (41,5 pct) (30,5 pct) (17,5 pct) IPSOS-Mora y Araujo 38,4 pct 25,3 pct 17,1 pct (42,7 pct) (28,1 pct) (19,0 pct) Ricardo Rouvier S/D S/D S/D (41,2 pct) (31,1 pct) (19,9 pct) (Reporting by Richard Lough, Maximiliano Rizzi and Nicolas Misculin; Editing by Grant McCool)
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