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Venezuela's Supreme Court has issued decisions shaking up the leadership of two small political parties, potentially preventing them from backing opposition presidential candidate Henrique Capriles.

The court's decisions, which call for immediate changes to the leadership of the parties Podemos and PPT, drew a sharp rebuke on Friday from one prominent party leader as well as criticism by the opposition.

Ismael Garcia, who was pushed aside as leader of Podemos, blamed President Hugo Chavez for the court's actions.

"The government isn't going to expropriate us," Garcia said in a televised speech as supporters cheered, saying party members still back Capriles regardless of the court's ruling.

Capriles condemned the legal decisions, saying that Chavez's government is resorting to desperate tactics to keep the two parties from supporting his candidacy. Both used to be pro-Chavez but have moved to the opposition.

Chavez's critics have repeatedly accused the president of wielding undue influence over the judiciary and using it to go after his adversaries. Chavez has denied those accusations.

"They're judicial tricks, the use of power to politically favor one option," Capriles said Friday in an interview with the TV channel Venevision. "Why does the court have to be deciding on organizations and political parties?"

In the case of Podemos, Capriles said, "in the end the decision is to prohibit them from nominating Capriles as candidate for president. That was the only objective of that decision."

Capriles had said Thursday on Twitter that most members of the two parties will remain with him regardless of the decisions.

The Supreme Court said in a statement on its website Thursday that it had decided to recognize former pro-Chavez state governor Didalco Bolivar as the leader of Podemos, rather than established leader Garcia, a vocal government critic.

A similar ruling in the case of PPT was announced by the court on Wednesday. It voided the party's most recent internal elections, which were carried out in October, and ordered it to hold new elections within 90 days.

The decisions could prevent the parties from backing Capriles before a Monday deadline for parties to specify the presidential candidate they will support.

Podemos broke with Chavez's government in 2007. PPT, which in Spanish stands for Fatherland For All, similarly has irked Chavez's government by defecting from its camp.

On the ballot in Venezuela, candidates' photos typically appear along with the symbols of parties that back them.

"We're the face of Podemos, and if you all put the faces of your political hit men and yours there... that will only be rejected by the people," Garcia said. "We represent it and you're not going to be able to change that."

The court's decisions drew criticism from others as well. Gustavo Hernandez Acevedo, a blogger writing on the website Caracas Chronicles, said the ruling "showcases just how far Hugo Chavez is willing to go to punish those he sees as traitors."

In the case of Podemos, the Supreme Court said in a statement that it had decided to review an earlier decision by its Electoral Chamber, which in March had denied a challenge by Bolivar to an agreement by party leaders to postpone internal elections.

The court said that Bolivar will lead the party "until the current case is dealt with in depth." That means Bolivar is to have the last word on which candidate the party will back in the presidential election, and he is expected to support Chavez.

Bolivar, a former governor of Aragua state, previously faced corruption charges and has changed political loyalties. He split with Chavez in 2007 when the governor refused to participate in the president's plan for various parties to join together in a single pro-government party.

In 2009, Bolivar was summoned for arraignment on corruption charges and sought asylum in Peru, saying he was being targeted for political reasons. He then returned to Venezuela in August 2011 saying he would face justice. He was jailed but later freed.

Capriles has the backing of a coalition of opposition parties. He was chosen in a February primary to be the opposition's single challenger to take on Chavez.

Capriles and Chavez both plan to formally sign up as candidates on Sunday and Monday, respectively, as they prepare for the Oct. 7 presidential vote.

The leftist president, who was first elected in 1998, is seeking another six-year term. He has recently scaled back his public appearances after undergoing cancer treatment in Cuba, and the race so far has been dominated by speculation about whether his illness may interfere with his re-election bid.

Capriles has been trailing in the polls, with survey results varying widely. Some polls touted by the government have given Chavez a lead of more than 20 percentage points, while others indicate a smaller margin for the president, some less than 5 percentage points.