BUENOS AIRES, Argentina (AP) — Frustration over a bruising economic crisis and rising poverty has eroded support for Argentina's pro-business incumbent ahead of Sunday's presidential election and boosted a populist challenger whose victory would mark a tilt to the center-left in a region rocked by political upheaval.

Polls have President Mauricio Macri trailing Peronist party candidate Alberto Fernández, whose surge has rattled financial markets and drawn attention to a possible return of his vice presidential running mate - ex-President Cristina Fernández.

Macri took office in 2015 promising to root out corruption and eliminate poverty but is now seeking a second term amid a sharp depreciation of Argentina's peso and soaring inflation.

He is shouldering most of the blame from voters for the economic woes and they made their frustration clear in primaries in August.