But on Sunday, one year after her husband died of a heart attack, Mrs. Kirchner, Argentina’s first elected female president, completed a remarkable political turnaround. With about 81 percent of voting stations tabulated, she was leading with about 53 percent of the vote, while her closest challenger, Hermes Binner of the Broad Progressive Front, had about 17 percent. The ample margin would be enough to avoid a runoff and be the widest victory since democracy was restored in 1983.

In a speech late Sunday in Plaza de Mayo, Mrs. Kirchner called for national unity and thanked the “multitudes of young people” who supported her.

The economy emerged as the central issue on voters’ minds. By many measures Argentina is booming: the economy is expected to grow by 8 percent this year, the fastest growth in Latin America; employment has reached record levels; and the poverty rate has been cut by more than half since 2007, the government said. The country continues to benefit from heavy government spending, high commodity prices and strong demand from China for its agricultural products.

Still, by re-electing Mrs. Kirchner, 58, voters seemed willing to look past some troubling signs. Inflation has soared to over 20 percent in the past year, second only to Venezuela’s among major Latin American economies, economists said. And the government has continued to govern with a heavy hand and little tolerance for opponents, including among the news media.

Opposition candidates tried to seize on those issues but gained little traction with voters.

“This election really seemed to defy the normal rules of politics,” said Michael Shifter, the president of the Inter-American Dialogue in Washington. “But that is what happens when things are going well in the economy and there is a dearth of alternatives.”

The Argentine government has continued to insist that the inflation rate is less than 10 percent, but the International Monetary Fund and private economists say the government data is unreliable. The issue has resonated less with voters because salaries have roughly kept pace with inflation, thanks to the Peronist government’s tight relations with union chieftains.

Mrs. Kirchner, a former senator, was first elected president in 2007 with promises to continue the economic model employed by her husband, who steered the country out of financial collapse but decided not to run for re-election, supporting his wife’s candidacy instead.

Mr. Kirchner had hewed to a strategy of keeping Argentina’s currency, the peso, heavily devalued from its 1990s’ levels, a move that made exports more competitive and spurred growth in manufacturing. But it also entailed subsidies for food and fuel and spending on social programs to win lower-income voters.

The Kirchners were a political power couple that drew comparisons to Bill and Hillary Clinton. Mrs. Kirchner’s victory in 2007 spurred talk that the Kirchners would alternate as president for another 12 years.

With her emotional speeches and designer suits, Mrs. Kirchner appealed to the masses, especially the working classes, the power base her husband had built.

During her campaign in 2007, Mrs. Kirchner vowed to re-engage Argentina with the international community, which Mr. Kirchner had largely eschewed while in office. He cut off talks with the International Monetary Fund after Argentina defaulted on $95 billion in foreign debts.

But the promised détente did not materialize, and foreign investors stayed away, especially after signs emerged that the government’s statistical agency was doctoring economic data, including the inflation rate.

As a result, Argentina has remained largely unable to borrow abroad, and it receives relatively little foreign direct investment, lagging behind Colombia and Peru and receiving less than half the amount flowing into Chile, according to the United Nations Economic Commission for Latin America and the Caribbean.

“Argentina is kind of an outlier in the region — a post-authoritarian, democratic government that has not embraced the principles of macroeconomic stability in the same way that Chile, Brazil and Uruguay have done,” said Cynthia Arnson, director of the Latin American program at the Woodrow Wilson Center in Washington. “That has been a huge disincentive to foreign investment.”

While Brazil’s star has risen, Argentina’s regional and international profile “has diminished dramatically” under the Kirchners, said Riordan Roett, the director of the Latin American program at Johns Hopkins University. “They carry no geopolitical weight.”

Still, despite predictions that the economic model would collapse, the economy grew by 9.2 percent last year. Mrs. Kirchner’s approval ratings began to climb even as the government accused the country’s largest media group, Clarín, of bias and fined private economists who disputed official economic figures.

Then, in October 2010, when Mr. Kirchner, who had suffered from heart problems, died, an outpouring of sympathy followed and Mrs. Kirchner’s approval ratings rose. She began to soften her public image, calling for unity and dialogue, a shift that won over more of the middle class, which had grown weary of the government’s authoritarian style, said Roberto Starke, a political analyst in Buenos Aires.

Meanwhile, the opposition failed to unite behind a candidate. Rivals like Eduardo Duhalde, a dissident Peronist, and Ricardo Alfonsín, a senator and son of Raul Alfonsín, the first civilian president after the dictatorship, divided the anti-Kirchner vote.

“None of them could get any traction with the government’s vulnerabilities — corruption and cronyism,” Mr. Shifter said.

As a result, the election became a referendum on the economy, analysts said.

Argentina’s continued success relies on commodity prices remaining high and on strong demand from China and Brazil, but economists say those factors may soon be undermined by the global economic downturn. Growth is expected to slow to 4.6 percent next year, in line with the rest of the region, but inflation may remain stubbornly high, economists said.

“When the money runs out, there will be a political reckoning,” said Karen Hooper, an analyst at Stratfor, a global intelligence company in Austin, Texas.

**Charles Newbery contributed reporting.