Venezuela vote race starts, Chavez foes eye gains

* Legislative vote test of Chavez support ahead of 2012

* Opposition gains assured after boycott five years ago

* Crime tops agenda as campaigns launched

By Frank Jack Daniel

CARACAS, Aug 25, (Reuters)- Venezuelan President Hugo Chavez and his opponents launched campaigns on Wednesday for legislative elections that test the socialist's support after a year of recession and will give his critics a louder voice.

Buoyant Chavez supporters organized parties and fireworks around Caracas after midnight to kick off a race dominated by criticism of the government's record on tackling Venezuela's appalling murder rate.

"Let's go to battle!" Chavez's campaign chief Aristobulo Isturiz bellowed at one raucous nocturnal rally.

Struggling opposition parties are all but guaranteed gains in the Sept. 26 vote after they boycotted the last election for lawmakers five years ago, leaving parliament in the major U.S. oil supplier entirely in the hands of the president's allies.

The elections -- a barometer of backing for Chavez's policies ahead of a presidential vote in two years -- are also a chance for opponents to take back a little of the power he has accumulated over more than 11 years in office in the OPEC nation.