(Recast with exit poll results)
By Hugh Bronstein
BUENOS AIRES, Aug 9 (Reuters) - Ruling party candidate Daniel Scioli was ahead in Argentina's presidential primary on Sunday, according to TV exit polls that showed voters tending toward the Buenos Aires governor's policy of gradual change after eight years of leftist government.
Scioli is in outgoing President Cristina Fernandez's Front for Victory party, and has said he favors slowly changing her policies, which include heavy state control of the economy.
The presidential election, in which Fernandez is banned from running for a third consecutive term, is on Oct. 25. Running second in Sunday's primary was Mauricio Macri, the business-friendly mayor of the capital city whose goal is to do well enough in the October vote to force a November run-off.
The primary is set up for each party to choose its presidential candidate, but with voters free to cross party lines, Sunday's vote will be a dry run ahead of the October election.
Both leading candidates are former businessmen with more orthodox policies than Fernandez, whose high public spending has drained fiscal accounts and fueled inflation while currency and trade controls slowed investment.
Macri promises to quickly free the markets. Scioli says "gradualism" is the best way to open the economy while preserving the strong social safety net weaved together by Fernandez since she first took power in 2007.
Macri competed with two much less popular members of his Cambiemos, or "Let's Change," coalition in Sunday's vote. Scioli ran unopposed in the Front for Victory primary.
Argentine stock and bond prices will likely fall if Scioli comes out of Sunday's primary strong enough to win the presidency in October's first round. If Macri looks strong enough to force a run-off in November, markets are set to rise.
To win outright in October, a candidate needs 45 percent of votes cast or 40 percent with a 10-point margin over the second-place candidate.
It was a rainy day in much of Argentina, which is good for crops in the world's No. 3 soybean exporter but complicated voting in some farm areas of breadbasket province Buenos Aires. Scioli said road crews were at work to ensure voters in rural areas hard hit by the rain could get to their polling stations.
He said he expected preliminary primary results by late Sunday night. "By about 10 p.m. (0100 GMT Monday) we should have a clear perspective," he told reporters.
Ignacio Labaqui, who analyses Argentina for Medley Global Advisors, said Macri's coalition needs at least 30 percent on Sunday to stay in serious contention.
Macri vows to scrap currency controls and grains export curbs, and to negotiate an end to the U.S. court battle with holders of non-paying sovereign bonds that has hobbled Argentina's finances by keeping it in default.
Scioli has revealed few details of his program, as he treads gingerly to lock in Fernandez's left-leaning base without alienating the wider electorate.
Fernandez's policies have fueled one of the world's highest inflation rates, but poor voters who have benefited from state largesse over the last eight years remain loyal to her. While barred from running for a third consecutive term in October, Fernandez could return as a presidential candidate in 2019. (Additional reporting by Jorge Otaola; Editing by Eric Walsh and Chris Reese)