Macri succeeded her in office with pledges to boost the economy with liberal policies, but was forced to seek a record US$56-billion bailout from the International Monetary Fund and raise interest rates to more than 60 percent following a currency crisis past year.
"I am sure that today we Argentines begin to build a new history", Fernandez said on Sunday.
"This is an election where Argentina has to determine whether it continues on a path of transformation, of deepening democracy, of insertion into the world, of improvement and development - or returns to an authoritarian populist model that has failed in all places where it has been implemented", he said.
Argentina's main political parties had already chosen their presidential nominees, allowing the primary to serve as a first concrete measure of voter sentiment. "We are living a fictitious economy and the government is not giving answers", he said in a radio interview Monday morning. Markets were taken by surprise as polls were predicting a tight race; instead, Macri found himself lugging 16 points behind the opposition. He has proposed an economic and social pact to combat inflation, which is running at 55 per cent.
The primary elections to select presidential candidates occurred two months ahead of the first round of the general elections scheduled for October 27. He says he is taking the necessary, painful steps to get the economy going after 12 years of leftist populism under Cristina Fernandez and her predecessor and late husband, Nestor Kirchner.
Fernandez, regarded as a moderate within the Peronist movement, has said he would seek to "rework" Argentina's $57-billion standby agreement with the International Monetary Fund if he won the general election.
However in his victory speech on Sunday, Fernandez also said that Cristina Kirchner and him were not looking back to "restoring" the past, but rather to a new Argentina where Argentines could again be happy, with jobs and money in their pockets.
Alberto and Cristina Fernandez, who are not related despite sharing the same surname, have blamed Macri for a rise in poverty and unemployment.
Argentina's central bank intervened, selling $105 million in the foreign exchange market to defend the peso in the face of the massive sell-off.
The country's main stocks index posted its worst day ever with all its components well in the red, while the cost of insuring exposure to Argentina's sovereign debt surged nearly 1,000 basis points. Markets are also anxious over de Kirchner, whose years as president from 2007 to 2015 were marked by a balance of payments crisis, interventionist state policies, currency controls and protectionism.
Will Alberto be able to do something similar with his mentor, the Lady, or will he fall a prisoner of Cristina and her populist inclinations.