First lady Cristina Fernandez de Kirchner will become Argentina's first elected woman leader, after easily winning a presidential vote largely centered on her husband's economic successes.
Ms Fernandez's margin of victory, seen as the largest in the history of Argentine democracy, will allow her to avoid a runoff vote next month.
With ballots counted at 96 per cent of polling stations, Fernandez had 44.86 per cent support, followed by another female candidate, former lawmaker Elisa Carrio, who had 22.98 per cent and conceded defeat late on Sunday.
"This is a triumph for all Argentines," Ms Fernandez told cheering supporters at her campaign headquarters, in a message that also acknowledged the challenges that lie ahead.
"Instead of putting us in a position of privilege, it gives us bigger responsibilities and greater obligations," she said, as her husband, President Nestor Kirchner, looked on.
The ruling Front for Victory coalition, an offshoot of the Peronist party, secured a majority in both houses of Congress and dominated in the election of eight provincial governors.
The Kirchners are Argentina's undisputed power couple and have been called "the Clintons of the South."
Ms Fernandez, a 54-year-old lawyer, is one of her husband's key aides and a longtime senator. Voters weary of Argentina's repeated boom-and-bust cycles hope she will advance the economic course set by her husband.
After a deep 2001-02 economic crisis, South America's second-largest economy has expanded at China-style rates since Mr Kirchner came to office four years ago. Growth has topped 8 per cent a year, driven by strong consumer spending and agricultural exports.
But even as Ms Fernandez inherits the economic boom overseen by her husband, she also faces mounting concern about high inflation, energy shortages and a growing perception among some Argentines that the Kirchners may have accumulated too much power.
"Cristina said the votes for her represent an enormous challenge and responsibility. Opposition leaders should feel the same challenge and responsibility to build an alternative ... and needed balance in this poor but noble democracy," columnist Eduardo van der Kooy wrote in leading daily Clarin.
Argentines, still stung by bouts of hyperinflation in the 1970s and 1980s, have expressed concern about climbing prices and recently called for boycotts of tomatoes, potatoes and other foods as prices have soared.
Results showed Ms Carrio, an anti-corruption crusader who campaigned on pledges of strengthening the country's fragile institutions, fared especially well with middle- and upper-class voters in several of Argentina's biggest cities, beating Ms Fernandez in Buenos Aires.
"There's a sector of public opinion, especially in urban areas, that's expressing discontent (with the Kirchners)," said Sergio Berensztein, an analyst at the polling group Poliarquia.
Much of Ms Fernandez's support came from Argentina's poor and working classes in Buenos Aires province, the country's most populous, and the impoverished northern provinces, where many credit Kirchner with generating jobs.
In her victory speech, Ms Fernandez appealed for Argentines' support. "We know it's necessary to deepen the changes and to do that, we need to rally the biggest number of Argentines to help us," she said