Mexico City ? Leftist candidate Andres Manuel Lopez Obrador said Sunday he was digging in for a long battle to ensure his ruling-party rival is not declared the winner of presidential elections, calling on supporters to demonstrate in front of the court that ruled against his demand for a full recount.

Lopez Obrador told tens of thousands of followers in Mexico City’s main Zocalo plaza that they should indefinitely man the sprawling, week-old protest camps that have brought much of the capital’s normally thriving center to a halt. The blockades have snarled traffic, costing the city an estimated $23 million a day.

The former Mexico City mayor said that he would continue to demand a full recount in the presidential race, despite the Federal Electoral Tribunal’s decision Saturday in favor of a partial recount. Electoral officials across the nation will begin sifting through ballots from 9 percent of the nation’s 130,000 polling places on Wednesday, wrapping up their work by the weekend.

An official count from the July 2 vote found that conservative Felipe Calderon of President Vicente Fox’s National Action Party beat Lopez Obrador by less than 0.6 percent, or about 240,000 votes.

On Sunday, Calderon said Mexico’s institutions were strong enough to survive attacks from “anti-democrats,” an apparent stab at the leftist protest movement.

“The solidness of our institutions has overcome the attacks of anti-democrats, anarchists and intolerance,” Calderon told a gathering of his party’s elected lawmakers.

Lopez Obrador asked his supporters to gather in front of the tribunal this evening, likely halting traffic on yet another main Mexico City street. He said he would demand the court “correct” its decision.

Before Lopez Obrador’s speech, protesters chanted in favor of seizing Mexico City’s airport. Some suggested taking over Congress, a move that would almost certainly trigger confrontations. Security has been increased at both facilities.

While Lopez Obrador did not say whether he would eventually approve such actions, he did promise “new actions, new measure of civil resistance.” He asked his followers “to prepare ourselves for a struggle that may last longer.”

Late Sunday, the leftist’s supporters brought a new element to their nonviolent protests, with thousands standing hand in hand to form a human chain along miles of roads in the heart of the capital.

The Mexico City government, controlled by Lopez Obrador’s Democratic Revolution Party, has protected the protest camps that have blocked the elegant Reforma Avenue and the Zocalo.