CARACAS, Venezuela (AP) — Venezuela's political standoff deepened Wednesday as anti-government demonstrators began gathering for a mass protest after congress voted to open a political trial against President Nicolas Maduro, hoping to drive the unpopular socialist leader from office.

Some schools and shops were shut in Caracas Wednesday as demonstrators marched toward key points around the city to back a recall campaign against Maduro.

Electoral authorities blocked the recall last week, and the faceoff escalated on Tuesday when the opposition-led legislature voted to hold a political trial of the president, accusing him of violating constitutional order.

That trial would have little legal effect since the constitution does not give congress power to oust the president and Maduro still controls other branches of government, including the military and Supreme Court, which has already declared the National Assembly illegitimate.

Opposition legislators argued that Venezuela's leader has effectively abandoned the presidency by neglecting his job. Several also questioned whether he was a dual Colombian national and therefore ineligible to hold Venezuela's highest office — an old, unproven claim.

Unlike other countries in Latin America such as Brazil, where Dilma Rousseff was removed from the presidency in August, Venezuela's National Assembly can't impeach the president. That decision lies squarely with the Supreme Court, which has never voted against Maduro.

Maduro, speaking at a rally Tuesday, accused opposition lawmakers of behaving like members of a "circus" and trying to carry out a "parliamentary coup."

"The National Assembly has been transformed into a bastion of evil and bitterness. It is useless to the interests of our country and our people," he told thousands of mostly state workers outside the presidential palace upon arriving from a six-day tour of the Middle East and Europe. "It has a single goal: to damage Venezuela."

In western Venezuela, students clashed with security forces for a second day on Tuesday. In the Andean town of Merida, police used tear gas to squash a small group of protesters that had blocked a major road, injuring eight people, according to reports on social media.

Even as tempers flare, the government and opposition have agreed to embark on an attempt at dialogue to defuse the crisis.

The talks, being sponsored by the Vatican and other South American governments, are set to begin Oct. 30 in the Caribbean island of Margarita. Maduro, who met with Pope Francis privately at the Vatican on Monday, said he will travel to Margarita to personally launch the talks.

But the two sides have gone down this road before during previous crises, and the opposition has scant hope for a breakthrough. Although Venezuelans overwhelmingly blame Maduro for food lines and triple-digit inflation the ruling party is in firm control of institutions like the military and has shown no interest in yielding to the opposition.

Defense Minister Gen. Vladimir Padrino, who many had been looking to as a potential brake on Maduro, spoke to the nation Tuesday dressed in camouflaged fatigues and surrounded by the top military command urging dialogue but calling on the opposition to respect the constitution.

That prompted an angry rebuke from National Assembly President Henry Ramos, who during the special session accused the military man of abandoning his constitutional duty to uphold Venezuela's democracy.

"How can he talk of respecting the constitution if he has become the foremost pimp of this regime's violation of the constitution," Ramos said, challenging security forces to arrest him when he attempts next week to travel to Washington to denounce Maduro's latest power grab.

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Joshua Goodman is on Twitter: https://twitter.com/apjoshgoodman His work can be found at http://bigstory.ap.org/journalist/joshua-goodman