BUENOS AIRES - Argentine Senator Gabriela Michetti will be the running mate of presidential candidate Mauricio Macri, he said on Friday, defining the battle lines ahead of an October election that will pit the business-friendly duo against the current ruling party.

Mauricio Macri (R), Buenos Aires' City Mayor and A
Mauricio Macri (R), Buenos Aires' City Mayor and Argentina's presidential contender walks alongside Senator Gabriela Michetti after he inaugurated a portion of a freeway in Buenos Aires, June 19, 2015.

Macri, mayor of Buenos Aires, is second in the polls against front-runner Daniel Scioli, the provincial governor who this week picked a member of the inner circle of outgoing President Cristina Fernandez as his vice presidential candidate.

"My running mate will be Gabriela Michetti," Macri said on Facebook.

The senator got her start in politics in 2003, years after being left in a wheelchair by an auto accident.

A charismatic campaigner, the 50-year-old Michetti is popular among middle class voters and may attract support from outside Macri's urban professional base.

"She's a testament to the values we want to bring to politics," he said.

Michetti has been a stalwart of Macri's Republican Proposal (PRO) party during her 12 years in politics.

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