Each morning, the seven judges who will decide Mexico's disputed presidential election are chauffeured into their gated office compound past a crowd of Andres Manuel Lopez Obrador's angry supporters.
"Where are our votes -- in the garbage?" says one of the banners demanding that the Federal Electoral Tribunal overturn Felipe Calderon's narrow victory in the July 2 vote and certify Lopez Obrador as president-elect.
It has been 10 years since the current tribunal was created to police an electoral system long plagued by blatant fraud. In that time, the tribunal has nullified 17 local, state and congressional elections and ruled against each of Mexico's three major parties in roughly equal proportions.
But the judicial arbiter of Mexico's young democracy has never faced a challenge like this.
With tens of thousands of protesters backing him in the streets, Lopez Obrador, of the leftist Democratic Revolution Party, or PRD, is asking the tribunal for two rulings that would stretch legal precedent.
Publicly, he is calling for a recount of all 41 million votes, in the hope of erasing his 244,000-vote deficit.
The motion his lawyers filed this week also seeks a ruling that President Vicente Fox's government tilted the playing field for Calderon, the candidate of Fox's conservative National Action Party, or PAN.
A favorable ruling on that motion would open the election to annulment and force a new one.
Calderon's legal team is contesting both motions. By law, the tribunal, which is scheduled to begin hearing the case next week, must resolve the motions by Aug. 31 and declare a winner by Sept. 6.
The decision, and whether it is accepted by both parties, will be a crucial test of whether Mexico can resolve disputes in a peaceful, legal manner rather than through the street demonstrations and backroom deals that settled close elections in the early 1990s.
At stake, too, is the prestige of this country's most trusted public institution after the army. In a country struggling to establish rule of law, the tribunal's authority stands out: The losers have always respected its decisions.
The tribunal was insulated from pressure when established in 1996. The 65 nominees vetted by the Supreme Court had to be free of political affiliation. The three big parties negotiated that list to seven -- five career judges and two legal scholars -- for election by a unanimous Congress.
They were given nonrenewable 10-year terms and, to discourage attempts to bribe them, the highest salaries of any Mexican public official -- about $415,000 a year.
The court has settled more than 20,000 electoral disputes; overruled banking secrecy laws in search of illegal campaign donations; and levied multimillion-dollar fines on electoral scofflaws.
In 2000, it nullified a 7,000-vote victory by the Institutional Revolutionary Party, the PRI, in Tabasco state. The tribunal found that the incumbent PRI governor had rigged the process in favor of his protege: Rival candidates got almost no media coverage, their mailed campaign literature was intercepted, voters were bribed and coerced.
That landmark ruling established the court's readiness to go beyond vote-tallying disputes and use "abstract causes" of unfairness to void an election -- one of the principles Lopez Obrador is now embracing.
In subsequent rulings, the tribunal caused riots among PRI supporters by removing a PRI-stacked state electoral board in Yucatan. It nullified the triumph of the PAN's congressional candidate in Michoacan state, ruling that he had violated the principle of church-state separation by portraying the Virgin of Guadalupe on his leaflets.
Todd A. Eisenstadt, an American University professor and author of a 2004 history titled "Courting Democracy in Mexico: Party Strategies and Electoral Institutions," said the tribunal's rulings show a consistency that protects the judges from claims of bias.
The judges have built "a very strong canon of electoral law on what used to be a quagmire of fraud," he said.
That record is a rough guide to how the judges might rule on the presidential race: They have been willing to recount ballots, but only selectively.
Lopez Obrador is asking for much more, however, and he has pointedly refused to say whether he would accept defeat.
Lopez Obrador's 836-page legal challenge alleges that the PAN exceeded campaign spending limits, used funds diverted from the treasury, pressed poor voters to back Calderon by threatening to cut off public welfare benefits, slandered Calderon's opponent in televised ads, and benefited from Fox's refusal to abide by a ban on his involvement in the campaign.
The legal drama is heightened by the tribunal's record of 4-to-3 splits on key rulings.
Many legal scholars think the tribunal will refuse to order the blanket recount Lopez Obrador wants -- the court has always rejected such requests -- and will balk at annulling the election.
If it grants either request, "that would be taking 10 years of jurisprudence and throwing it out overnight," said Cesar Nava, head of Calderon's legal team. He will argue that the court has no authority to annul a presidential election and that any recount should be limited to ballot boxes whose tally sheets are specifically challenged as irregular.
When Lopez Obrador's PRD lost a close race for governor of Guerrero in 1999 and staged boisterous protests, for example, the tribunal opened a sample of ballot boxes, just enough to determine that a full recount would not make a difference.
In June, anticipating a close finish in the presidential race, Leonel Castillo, the panel's chief magistrate, told Milenio magazine, "Some may ask for a total recount, but when that petition arrives, we're going to say no."
The tribunal's position on Lopez Obrador's challenge to the fairness of the election is less predictable.
The tribunal often acts boldly, beyond the letter of electoral law, to uphold the broader constitutional principle that voters enjoy the rights to choose leaders in equitable contests.
Judges Castillo and Mauro Miguel Reyes Zapata championed the 2000 Tabasco precedent of voiding a state election in the case of extreme inequity. They were backed in that ruling and subsequent ones by three colleagues. But the panel's majority has wavered over the years, letting some less-tainted elections stand.
The remaining two judges, Eloy Fuentes and Alfonsina Navarro, dissented from the Tabasco decision.
Another issue is whether the panel can annul a presidential election. John M. Ackerman, a legal scholar at the National Autonomous University of Mexico, said the panel's power to nullify elections was explicit only for state and local races.
The spectacle of mass rallies planned by the PRD, already visible in microcosm at the tribunal's doorstep, will oblige the judges to think beyond legalities and weigh political fallout, observers of the court say.
Jesus Cantu Escalante, a former electoral official, said the judges might balk at forcing a new election with the country so polarized.
Author Eisenstadt said, "That will make them stick within the band of discretion they have established in previous cases.
"Going outside of that and establishing new grounds of activism could have some destabilizing effects, and I think they're going to avoid that at all costs."