Argentina's conservative opposition party is expected to win Sunday's mayoral run-off election in Buenos Aires, retaining its power in the capital ahead of presidential voting later this year.

With Buenos Aires' 2.5 million voters accounting for nearly 8 percent of Argentina's voting population, its election is closely watched for tendencies for the presidential primaries and the Oct. 25 national election.

Favored to win Sunday is business-friendly PRO Party candidate Horacio Rodriguez Larreta, who has 50 percent support, according to the average of three recent surveys by local pollsters. His rival, ECO Party candidate and former economy minister Martin Lousteau, trails with 40 percent support.

Rodriguez Larreta, 50, is the chief-of-staff of outgoing mayor and possible presidential candidate Mauricio Macri. Rodriguez Larreta won a July 5 round of mayoral voting, but did not garner enough votes to avoid a run-off against the 44-year-old Lousteau.

Voters in Buenos Aires often pick mayors from parties that oppose the president. Both Rodriguez Larreta and Lousteau are critical of President Cristina Fernandez's government.

Fernandez's Frente para la Victoria coalition is seen as trailing too far behind to be considered a contender in the capital's election.

Rodriguez Larreta has said he hopes to help achieve change for all of Argentina after the 12-year leftist rule of Fernandez, and her late husband and predecessor, President Nestor Kirchner.

A victory by the PRO would improve Macri's chances of achieving the presidency. His main rival is Buenos Aires Gov. Daniel Scioli, who has been picked by Fernandez to continue the populist policies that began with her husband's presidency. Fernandez is barred from seeking a third consecutive term.

Restoring Argentina's sense of pride and sovereignty after the country's worst economic crisis in 2001 has been the central goal of Fernandez and Kirchner. The presidential couple negotiated or paid off most of Argentina's defaulted debt, nationalized the pension system, kept energy cheap through subsidies and dug deep into the treasury to redirect revenue to the poor through handouts.

But many Argentines are calling for change amid frustration with one of the world's highest inflation rates, government currency controls and corruption accusations that have penetrated deep into Fernandez's inner circle.