* Legislative vote tests Chavez support ahead of 2012
* Opposition gains assured after boycott five years ago (Adds polling numbers, more details on rallies)
By Frank Jack Daniel
CARACAS, Aug 25 (Reuters) - Venezuelan soldiers fired tear gas at opposition candidates on Wednesday at the start of campaigning for legislative elections that will test support for President Hugo Chavez amid a recession and high crime.
Struggling opposition parties are all but guaranteed gains in the Sept. 26 vote after boycotting an election for lawmakers five years ago, leaving the major U.S. oil supplier's national assembly entirely in the hands of the president's allies.
National Guard soldiers, who have policing powers, used tear gas to repel a small group of opposition candidates near the legislature on a busy downtown street, TV images showed, after they appeared to clash with parliament workers.
"We were walking towards the assembly. We were going to read a document, and without warning the National Guard started firing tear gas," candidate Stalin Gonzalez told opposition TV station Globovision. The parliament issued a statement accusing the candidates of trying to force their way into the building.
Elsewhere, thousands of bouyant Chavez supporters dressed in the Socialist Party's signature red color flocked to large rallies across the country of 30 million people to kick off a race the president dubbed "Operation Demolition." Pre-campaign debate has been dominated by criticism of the government's record on tackling Venezuela's murder rate.
"Let's go to battle!" Chavez's campaign chief Aristobulo Isturiz bellowed at one raucous rally.
The elections -- a barometer of backing for Chavez's policies ahead of a presidential vote in two years -- are a chance for opponents to take back some of the power he has accumulated over more than 11 years in office. <^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Despite sky-high crime and economic woes, Chavez remains Venezuela's most popular politician, helped by social spending. But the ex-soldier, who has also polarized the country between backers of his policies favoring the poor and those who call him a dictator, has seen his ratings dive this year.
Opposition parties have fielded unity candidates to increase their chances of denting Chavez's grip on parliament.
They hope to capitalize on his relative weakness after months fighting crises such as electricity cuts and a scandal over rotting food that dragged on his ratings.
Pollster Saul Cabrera of Consultores 21 on Wednesday said his most recent survey conducted in July showed Chavez's popularity down 7 points this year to 36 percent. Other polling firms tend to put Chavez's popularity slightly higher, but they have also shown a ratings downturn this year.
Most analysts expect Chavez's socialist party to lose seats but still hold its majority, helped by changes to electoral districts that critics call gerrymandering.
It is possible the socialists will end up with a majority of seats without winning a majority of votes, an embarrassing outcome for a populist leader such as Chavez.
There is a slim chance the opposition will win the most seats, which could cause political instability. Their goal is to win at least a third of the legislature and limit Chavez's ability to pass major legislation.
Usually an expert at setting the political agenda, especially ahead of elections, Chavez seems to have been caught off balance by an early campaign from opposition media to highlight the government's failure to tackle violent crime.
Venezuela has one of the world's highest murder rates with between 13,000 and 16,000 people killed last year, according to leaked police numbers and a non-governmental watchdog, respectively.
Last week a court ordered two newspapers not to publish violent pictures after they printed a gory archive photo of bodies piled up in a morgue. [ID:nN18125440]
The government, which also responded angrily to a New York Times story comparing Venezuela's violence to Iraq, says it is working hard to bring down crime and that a new national police force has slashed homicide rates in a Caracas pilot project.
A handful of lawmakers who defected from Chavez's ranks in 2007 are the opposition's only presence in the current parliament, giving Chavez legislative carte blanche.
He has used that power to start remolding one of the continent's most Americanized nations as a socialist society, while expanding his sway over courts and other institutions.
Critics say the 56-year-old ally of Cuba is following his mentor Fidel Castro and installing an autocratic communist dictatorship in the baseball-mad nation studded with fast food restaurants and shopping malls.
Chavez, who has lost just one of over a dozen elections since 1998, says he is a democrat committed to freeing Venezuela from U.S. dominance and local oligarchs. (Additional reporting by Eyanir Chinea, Patricia Rondon, Andrew Cawthorne; Editing by Andrew Cawthorne and Cynthia Osterman)