After four decades of alternating in power, Venezuela's traditional parties have been left fighting for survival on the fringes of the political scene by President Hugo Chavez's radical program for change.

"They must fight because they are facing extinction," said Alfredo Keller, who heads a Caracas consulting and polling firm. "But after so many years of history, it is very hard for them to understand that the rules of the game have changed."

Reflecting a sense of desperation, some lawmakers reiterated today that they will defy Monday's decision by the 131-member constituent assembly dominated by Chavez supporters to effectively shut down the elected Congress. They said they will try to reconvene anyway, in the Capitol if they are permitted. But it was unclear if they would be able do so or if the public would listen if they do.

"This government only wants to have an obedient parliament and that role will not be accepted by the Congress of Venezuela," said a statement from the parties that traditionally have managed the country, Democratic Action, the Social Christian Party and Project Venezuela. "We categorically reject the legislative intervention decree by the assembly because we consider it a violation of popular sovereignty and the Constitution."

Party leaders started to focus on ways to rebuild their weakened organizations, which lost their grip on power last December when Chavez won election by a landslide on a wave of widespread discontent over government corruption and mismanagement, which have allowed poverty to spread despite a profitable oil industry.

Congressional leaders said they hope to win renewed support by launching a campaign accusing the assembly and Chavez of acting illegally and running roughshod over civil liberties in carrying out changes that they contend are designed to concentrate power in the hands of the president, a cashiered lieutenant colonel who lead a failed coup in 1992.

"We are going to initiate a political rebirth by criticizing this militaristic project, talking about themes such as respect for civil laws and defending the decentralization of power," said Mireya Rodriguez, head of the Project Venezuela congressional faction.

Party officials also said they may cobble together political coalitions, building on a rare show of unity emerging among the main parties since Chavez ascended to the presidency, and seek the backing of other segments of society that oppose his program.

If Chavez supporters "continue to repress the democratic system and its institutions, we will have to unite the other players," said Cesar Perez, who heads the Social Christian congressional faction. "In the short term, it is possible there still will not be a response from the people . . . that we will not have a massive backing. But we will be present."

Alberto Franceschi, one of six opposition members in the assembly, agreed that coalition-building has possibilities. "There is a transformation process being carried out within the traditional parties. If this process is accomplished and brings new faces that are accepted . . . then why not unite?" he said. "This may or may not include an electoral bloc."

Party officials acknowledged, however, that concrete strategies to rejuvenate their organizations have been slow in coming, which they said is troubling since Chavez's populist proposals have been known for some time.

"They have to make a decision now. Do they silently nurse their wounds and accept whatever crumbs are thrown to them by [the assembly] or do they try to be a cause celebre and continue with righteous indignation and get an international arena for their grievances," said Eric Ekvall, a political strategist in Caracas. "Right now, Congress is like a deer caught in headlights."

Turning the tide of popular opinion will be a difficult task for the parties, which are largely controlled by the political figures who have been running Venezuela for years.

Chavez, 45, remains extremely popular with a 70 percent approval rating in recent polls despite a punishing recession and the loss of hundreds of thousands of jobs since he took office Feb. 2.

Many Venezuelans distrust the traditional parties and the political and legal systems in general. Leaders of the constituent assembly cite a World Bank survey that says 93 percent of Venezuelans have no faith in the justice system.

Claudio Fermin, a former presidential candidate and independent member of the assembly, added, "What is lacking in Venezuela are not political parties, it is new political attitudes."

In that vein, 150 activists, including Franceschi, gathered in Caracas on Saturday seeking to create an alternative political movement to Chavez's coalition. But that effort is just getting off the ground.