* Fernandez trounced opposition in Aug. 14 primary vote
* Many voters think only the Peronists able to govern
By Guido Nejamkis and Luis Andres Henao
BUENOS AIRES, Aug 22 (Reuters) - Argentina's opposition leaders are campaigning to retain their clout in Congress after President Cristina Fernandez's landslide primary election win dashed their hopes of taking the presidency.
Fernandez won 50 percent of votes in the Aug. 14 primary, which was seen as a dress rehearsal for the Oct. 23 election, considering that all political parties had already anointed their candidates and voters could choose among them. [ID:nN1E77E00L]
Fernandez's rivals argue there must be a balance of powers so that already-weak congressional controls on the executive branch do not disappear entirely.
"I'm going to campaign, but not to become president," anti-corruption crusader Elisa Carrio said after winning just 3.2 percent of votes in the primary. "I'm going to campaign ... so that (my party's) legislators enter Congress."
Fernandez came in a whopping 38 percentage points ahead of her two closest contenders, centrist Radical party congressman Ricardo Alfonsin and former President Eduardo Duhalde, a dissident member of the ruling Peronist party. They both received 12 percent of the vote.
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Fernandez lost control of Congress in 2009, a year after farmers staged months of protest against a tax hike on soy exports. Many middle-class Argentines perceive her as arrogant and frown on her interventionist economic policies.
But an economic boom since 2003 is giving Fernandez and other local office incumbents an undisputed edge this year.
She also received public sympathy after her husband and presidential predecessor, Nestor Kirchner, died last year.
She also benefited from infighting among the opposition.
"We voted for the opposition out of decency but they don't have many ideas. There are so many candidates, but they can't agree on anything," said Elena Somasa, a 63-year-old Radical party supporter.
Alfonsin admitted he was shifting his strategy.
"We're trying to convey that this election also involves other posts," he said. "Argentines should realize it's not good to concentrate all the state's powers in one party's hands."
In October's general election, voters will cast ballots for 24 senators and 130 lower-house legislators.
If voting patterns in October stay unchanged from the primary, analysts say the ruling party could win 86 lower-house seats, keeping its total representation at 106 seats. This is not far below the 129 seats needed for a quorum if the ruling party's allies are considered.
Most of the seats up for election are held by ruling party members. If 86 seats are won by the official party, it would mean that Fernandez's allies would win 19 new seats.
No one has a clear majority in the 72-member Senate, but the ruling party is the biggest minority block.
Thanks to the fact that some opposition senators have acted in favor of the government, Fernandez can get laws passed in the chamber after at times arduous negotiations.
Many Argentines are still licking their wounds from the country's 2001-02 political and economic crisis, when five presidents took office over the course of about one week after Radical party President Fernando de la Rua was forced out.
In this month's primary, nearly 70 percent of voters cast their ballots for a Peronist, between Fernandez, Duhalde and another dissident Peronist candidate, Alberto Rodriguez Saa.
"If you're not a Peronist, you can't win because they have a corrupt system and control the unions. They will topple your government," said Bernabe Garcia, 44, who works in public relations.
Argentina's poor -- who make up about one quarter of the population -- are grateful to Fernandez for child welfare benefits that she introduced.
And the primary showed that the opposition's proposals to ease state intervention in the economy received little support -- even in rural areas, where Fernandez's backing rebounded from rock-bottom levels in 2009.
"If people have enough money to buy a flat-screen TV, they don't care about anything else," said Hugo Biolcati, head of the Argentine Rural Society, which is critical of the government. (Writing by Hilary Burke, editing by Hugh Bronstein and Philip Barbara)