By Richard Lough
BUENOS AIRES (Reuters) - Pro-business Buenos Aires Mayor Mauricio Macri has ruled out forming an alliance with fellow opposition candidate Sergio Massa ahead of Argentina's October presidential election, Macri's campaign team said on Friday.
Speculation has swirled of a deal between the two to defeat the ruling Front for Victory party candidate, Daniel Scioli.
Scioli holds a wafer-thin lead over Macri in polls, as the clock ticks toward a June 10 deadline for parties to declare alliances.
Massa, a former cabinet chief to President Cristina Fernandez, left the leftist ruling coalition in 2013. His popularity has faded this year, and a tie-up with center-right Macri could strengthen the opposition.
A Massa spokesman said all options remained on the table. Macri's camp dismissed talk of a deal.
"They have already given all they have to give. We're betting on individuals who have no connection with the running of the country in recent years to lead Argentina with fresh ideas," Macri's campaign office said in an emailed comment.
Massa pitches himself as a centrist within the broad Peronist movement that has ruled Argentina for all but eight years since the return of democracy in 1983. But his campaign is faltering.
Massa has burned bridges with Fernandez loyalists, while many opposition and swing voters still associate the lawmaker with Fernandez's turbulent years in power. Some senior officials in Massa's Front for Renewal have defected back to the ruling coalition.
An opinion poll by Management & Fit in late May showed Scioli and Macri running neck and neck, almost 20 points ahead of Massa, who had 13.8 percent of voter support. In December, Management & Fit had Massa within 7.5 percent of Scioli. Other pollsters had him leading.
Both Scioli and Macri paint the presidential contest as a two horse race, although Scioli faces a test in his own party primary in August.
Rumors of an accord gained momentum on Thursday after Fernandez's cabinet chief, Anibal Fernandez, speculated Massa would run for governor of the powerful Buenos Aires province in an alliance with Macri.
"Nothing can be ruled out," a Massa spokesman said.
While a deal with Massa would raise Macri's profile in regions where he has little backing, it would weaken his claim to be the candidate of wholesale change. Many Massa voters could switch their support to Scioli rather than back a non-Peronist.
Macri "wants to run as a pure opposition candidate and represent a 'new political' movement," said Daniel Kerner of Eurasia Group.