By Helen Popper

BUENOS AIRES (Reuters) - Argentine President Cristina Fernandez looks set to win easy re-election on Sunday after a dramatic comeback that has confounded critics of her unconventional economic policies and combative style.

A center-leftist who has given the state a leading role in the economy, Fernandez has rebounded from low approval ratings and angry protests by farmers and middle-class voters that erupted early in her first term. Polls show she could win more than 50 percent of the vote on Sunday.

Argentina has one of the world's fastest-growing economies and despite high inflation and other signs of strain, the fiery Fernandez has a huge lead over a splintered field of opponents.

"She's got a lot of character, she faces up to challenges. There's no one in the opposition like that," said Romina Yerbas, 37, a bank employee in downtown Buenos Aires.

Lower international prices for soybeans, Argentina's top export, and a slowdown in neighboring powerhouse Brazil are fanning doubts about the sustainability of her big spending, high-growth policies, however.

Inflation estimated by economists at almost 25 percent is hurting poor families and driving up labor costs, fueling forecasts that Argentina may be heading for a hard landing during Fernandez's likely second four-year term.

But with unemployment at a 20-year low and middle-class Argentines still enjoying a shopping spree, few think she will be in a hurry to change tack. If she regains control of Congress, as expected, her hand will be further strengthened.

"She's unlikely to admit something is wrong with the current set-up and would probably position any new initiatives in terms of a more uncertain global outlook," said Michael Henderson, an economist at London-based Capital Economics.

The president's detractors say antagonistic policy-making and prickly ties with big business and the International Monetary Fund threaten to blacklist the country for good among investors.

A recent crackdown on economists whose inflation estimates double the official rate of a discredited state statistics agency is typical of Fernandez's controversial methods.

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She stunned financial markets by nationalizing private pensions in 2008, the central bank is run by a close ally and businesses are routinely strong-armed into price control agreements and deals to increase their exports.

"It's certainly one of the most market-unfriendly governments in South America ... only Venezuela and perhaps Ecuador could top them," Henderson said.

Among many Argentines though, who blame free-market policies for stoking an economic meltdown in 2001/02, Fernandez's willingness to tear up the rule book is popular.

Memories of the crisis are fresh in many voters' minds, and Fernandez, 58, often contrasts welfare spending and factory openings with the debacle that sank millions into poverty and culminated in the biggest sovereign debt default in history.

She says the country's industrial renaissance and consumer boom is thanks to the measures began in 2003 by her late husband and predecessor as president, Nestor Kirchner.

Kirchner's death of a heart attack a year ago prompted an outpouring of public sympathy. It also helped Fernandez dispel criticism he was running her government from the sidelines.

"It was as if she finally started her own presidency," said author and columnist James Neilson.

Still dressed in the black of mourning, a more conciliatory Fernandez dashes her speeches with sometimes-tearful tributes to Kirchner, who she has called "a visionary."

As well as keeping many of Kirchner's policies and advisers, the Peronist president inherited several of his feuds with perceived government enemies, notably the farmers.

Grains producers in Argentina's legendary Pampas grasslands complained for years about beef export curbs before Fernandez's tax hike on soy exports triggered massive protests in 2008.

When her approval ratings plunged to 20 percent as voters rejected the couple's handling of the conflict, some critics said it marked the beginning of the end of "Kirchnerism".

Investors had hoped this year's election might bring in a government more accommodating of their interests, but the opposition's failure to grab the initiative dashed such hopes.

"There's a sense that backing any opposition candidate would be a leap into the unknown," said sociologist Ricardo Sidicaro. "That's given Cristina support from voters who don't exactly like what she does, but recognize she can govern."

Polls give her a 40-point lead over her nearest rival, Socialist provincial governor Hermes Binner, who has gained a bit of ground since an August primary vote that set the stage for Sunday's election.

Fernandez won 50 percent of votes in the primary, which was effectively a dress rehearsal because all candidates had to take part and none faced competition within their own parties.

To win on Sunday without facing a run-off, Fernandez needs to win 45 percent of the vote, or just 40 percent with a lead of at least 10 percentage points over the nearest rival.

She is also hoping to regain control of Congress, which she lost at mid-term elections in 2009, when voters punished her over the farm revolt and a sharp economic slowdown.

"The ruling party could be the biggest bloc in the lower house," said Mariel Fornoni, a pollster at the Management & Fit consultancy. "Even if they don't manage that, they'll be in a position to control the house with their allies."

(Additional reporting by Alejandro Lifschitz; Editing by Kieran Murray)