Midterm elections Sunday dealt a tough new loss to Argentine President Cristina Kirchner's political movement in the country's biggest voting district, officials said.
Shirts with the portraits of Argentine President Cristina Kirchner, late president Nestor Kirchner and of Eva Peron are displayed for sale at Plaza de Mayo square in Buenos Aires on October 17, 2013
Exit polls cited by local television said her wing of the Peronist party would not win in Buenos Aires province, home to 40 percent of the nation's 30 million-plus voters.
It also stood to lose in the federal capital; the second city of Cordoba; and the cities of Santa Fe and Mendoza, the reports showed.
Opposition lawmaker Sergio Massa, mayor of Tigre and a former cabinet chief for the current president, defeated the Kirchner wing candidate in Buenos Aires province, the reports said after polls closed at 2100 GMT.
That makes Massa, 41, a likely presidential hopeful for general elections in 2015 -- Kirchner is not eligible to stand herself.
While Kirchner's wing of the Peronists was likely to remain the single largest political movement at federal level, it was not clear by late Sunday if they would hold on to majorities in both houses of Congress.
Voters were eligible to cast ballots to elect half the lower chamber of Congress and a third of the Senate.
The standard bearer of the populist-nationalist Peronists, Kirchner is barred from running for a third term in 2015 and many see Sunday's vote as the start of the race to replace her.
Her Front for Victory faction is expected to lose seats to both Massa's Peronist movement and to the divided right- and left-wing opposition parties.
A polarizing figure, Kirchner has seen her popularity sag in recent months, despite a health crisis which some thought might bolster her public support.
Her oldest son Maximo, told AFP that Kirchner on Sunday was "well, and in good spirits" after surgery this month to remove a blood clot on her brain.
She was not, however, quite well enough to cast a ballot, and continues to rest and heal at the presidential residence north of Buenos Aires.
Argentina's first democratically-elected female president, Kirchner has seen her approval rating slide to about 30 percent since she was swept back into office for a second term in 2011.
Mariel Fornoni, head of pollster Management & Fit, said the election was a key barometer of support -- or lack of it -- for the Argentine leader.
"It is a cycle that is ending, and a point of departure. Monday is the beginning of the race for the presidential election of 2015 and control of Peronism," Fornoni said.
Argentina's business class has been angered by Kirchner's failure to control inflation and protectionist economics, import restrictions, the nationalization of companies such as energy giant YPF and foreign exchange controls.
Critics are also skeptical of her foreign policy alignment with anti-Western governments in Bolivia, Ecuador and Venezuela.
But the poor revere the president for her fight against poverty, generous social welfare programs and improved retirement pensions.
A series of challenges, however, faces the country -- Argentina's economy is sluggish while violent crime is on the rise.
And although Argentina is still one of the world's breadbaskets -- exporting massive amounts of soy, wheat and meat -- Kirchner's government has presided over expanding market controls, and sky-high inflation.
Kirchner followed her late husband, Nestor Kirchner, as Argentina's president. Her husband was in office from 2003-2007.
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