Mexico's Enrique Peña Nieto officially declared election winner MEXICO CITY - Dismissing arguments that recent elections were rife with fraud, Mexico's electoral tribunal on Friday officially declared Institutional Revolutionary Party candidate Enrique Peña Nieto the president-elect, a ruling that was defiantly rejected by leftist leader Andres Manuel Lopez Obrador, the second-place finisher who, for the second presidential contest in a row, called his followers into the streets of the capital to protest. The unanimous ruling by the seven-judge panel clears the way for the return of Peña Nieto's party, known as the PRI, to power. It had lost the quasi-authoritarian grip on the country that it had enjoyed for more than seven decades in 2000, after numerous democratic reforms. Though there were scattered protests throughout Mexico City, they have not yet risen to the levels of 2006 when, after an even closer election, Lopez Obrador's followers choked the city center for weeks, bringing the country to the brink of a constitutional crisis. Lopez Obrador - who has declared the latest elections neither "clean, free or authentic" - has called for a protest Sept. 9 in the Zocalo, the capital's historic square. The president-elect arrived at the tribunal chambers late Friday to receive the judges' blessing. In a short speech, he urged Mexicans to unify despite their differences, and had words that, while not mentioning him by name, were obviously meant for his vanquished opponent: "Legality is fundamental to our democratic system," Peña Nieto said. "There are rules, deadlines and procedures," he said. All of the competitors accept them, and we have an obligation to respect them. The judges' decision was widely anticipated by observers here who had assumed that the tribunal would not deem the PRI's electoral sins sufficiently grave to warrant overturning an election that Peña Nieto won by nearly 3.2 million votes. In official complaints before the tribunal, Lopez Obrador's leftist coalition argued, among other things, that the PRI breached campaign spending limits; enjoyed an unsavory relationship with national media, resulting in biased coverage; and "bought votes" by handing out thousands of gift cards for use at chain department stores. In the end, however, tribunal judge Pedro Esteban Penagos stated that the leftist parties "did not provide proof ... that was of such magnitude that they would have the legal effect of invalidating the will of more than 50 million citizens." That did little to assuage Peña Nieto's detractors, who remained convinced that the PRI, as in times past, had worked the electoral system like a skilled pinball player, bumping the game in their favor, but never so egregiously as to trip the "tilt" lights. The most vehement protest came from Lopez Obrador, 58, the eternally feisty - or, as his detractors would have it, eternally querulous - figurehead of the Mexican left. On Friday, he declared that his opponent had cheated his way to victory. It was the same charge he leveled in 2006 against current President Felipe Calderon of the conservative National Action Party. "I am not going to recognize an illegitimate power derived from the buying of votes and of other grave violations of the constitution and the laws," he said. To do so, he added, "would imply a betrayal of millions of Mexicans who fight against pretense, and farce, and who are in favor of a true change." Numerous protests have clogged the streets of the capital since the July elections, many of them sparked by the Internet-fueled student movement known as Yo Soy 132. The group, which has vowed to remain peaceful, has also vowed to keep up the pressure. But so far the protests do not match the tumult of 2006. Some Yo Soy 132 members reportedly descended on the PRI headquarters in downtown Mexico City on Thursday, prompting a brief evacuation of the building. On Friday, television cameras showed some protesters at tollbooths on the highway between the capital and Cuernavaca. The Yo Soy 132 movement also pledged to march on the tribunal building later in the day. Lopez Obrador never accepted the results of the 2006 elections, which he lost by about half a percentage point. He even went so far as to participate in his own "swearing in" on the Zocalo, draping himself with the red, white and green sash that is the symbol of presidential power. This time, his margin of loss was more than 6 percentage points. And yet, as political analyst Jose Antonio Crespo noted, "in every way, [his] discourse is the same: 'There was fraud, and they robbed me of an election that I won.'" That stance, Crespo argued, leaves an ugly choice for the more moderate members of Lopez Obrador's Revolutionary Democratic Party as they seek to broaden the appeal of a party that has never won the presidency. If they decide to work with the president-elect, Crespo said, they probably will be labeled traitors by Lopez Obrador and his more emphatically left-wing followers. But if the moderates stay loyal to Lopez Obrador and refuse to share the burdens of governance, Crespo said, "they will go on alienating themselves from the independent voters who are the ones who decide elections." Cecilia Sanchez and Daniel Hernandez of The Times' Mexico City bureau contributed to this report.