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BUENOS AIRES (Reuters) - Argentina’s ruling party candidate for Senate in the key province of Buenos Aires is 4.8 percentage points ahead of the opposition candidate, according to a poll by consultancy Management & Fit sent exclusively to Reuters on Friday.

The country’s mid-term congressional election will be held this Sunday, and is seen as an early indicator of the electoral power that President Mauricio Macri will have going into his 2019 re-election campaign.

Esteban Bullrich, of Macri’s “Cambiemos” or “Let’s Change” party, is forecast to win 35.3 percent of votes in his bid for the Senate, according to the poll. Buenos Aires province is home to a third of Argentina’s population.

His opponent, former President Cristina Fernandez, has 30.5 percent of voter intentions, according to the Management & Fit survey of 2,000 voters. The poll had a margin of error of 3.3 to 3.5 percentage points.

Fernandez is loved by many low-income Argentines for her generous social spending. Macri, a proponent of free-markets, and Cambiemos have been criticized for reducing popular home heating and transportation subsidies but lauded by investors who say the President’s policies can return Argentina to sustained growth.