President Felipe Calderón, left, the outgoing president of Mexico, and Enrique Peña Nieto, the new leader, at a midnight handover ceremony on Dec. 1 in Mexico City.
MEXICO CITY — Enrique Peña Nieto became president of Mexico early Saturday, beginning a six-year term in which he has promised to accelerate economic growth, reduce the violence related to the drug war and forge closer, broader ties with the United States.
Mr. Peña Nieto took office at 12:01 a.m. in a short ceremony at the presidential residence with his predecessor, Felipe Calderón. Mr. Peña Nieto is scheduled to take the oath of office before Congress on Saturday morning and then deliver a speech before an audience of domestic and foreign dignitaries, including Vice President Joseph R. Biden Jr., with whom he will also meet privately.
Mr. Peña Nieto, 46, a lawyer who served as governor of Mexico State, has vowed to continue Mr. Calderón’s efforts to work with American law enforcement agencies to quell the violence linked to drug gangs that has killed tens of thousands in the past several years and tarnished Mexico’s image.
His team has emphasized the need to bolster Mexico’s economy, which rebounded from a recession in 2009 and is now growing faster than that of the United States, thanks to an infusion of new manufacturing plants and other investment.
His administration plans more steps to stimulate the economy, arguing that generating better-paying jobs will go a long way toward reducing violence by providing alternatives to crime for the chronically underemployed.
Mr. Peña Nieto also plans to reorganize the federal security forces and intends to form paramilitary units with police duties to combat violence in rural areas and support local and state police departments that are too corrupt or poorly trained to fight crime.
Still, his administration will be watched closely to see whether it is propelling Mexico forward or backward.
Mr. Peña Nieto ushers in a new era for the Institutional Revolutionary Party, known as the PRI, which ruled Mexico for more than 70 years before the more conservative National Action Party toppled it in 2000 and defeated it again in 2006.
But Mr. Peña Nieto and his associates said they represented a new, chastened party bent on promoting efficiency and economic change and promising to fight the kind of corruption long associated with it.
“It’s a very common misconception to think that the PRI’s return to power means the return of something that is already in history,” Luis Videgaray, who led the president’s transition team and will become treasury minister, said in a recent interview.
“The PRI of today is like any other party: a party that competes in a democracy, that accepts results and understands that only through good government would it be able to compete again in elections,” he said.
When Mr. Peña Nieto announced his cabinet on Friday, it was clear that he had relied largely on PRI stalwarts, including four former governors and a former mayor of Mexico City. But he also placed several young, foreign-educated technocrats from his inner circle, including Mr. Videgaray, in prominent positions.
The new president begins his term on a politically shaky foundation. He won 38 percent of the vote in the July election, and for weeks afterward, political opponents complained about what they said were voting irregularities. The PRI-led coalition is the largest in Congress, but it does not have an absolute majority and will need alliances to get anything done.
Hours before Mr. Peña Nieto planned to attend the swearing-in ceremony, protesters denouncing his legitimacy clashed outside the congressional building with riot police officers.
The police fired tear gas at the protesters, many of them affiliated with a youth movement objecting to the July election known as #YoSoy132, “I am 132,” who hurled rocks and bottles at the police and damaged metal barriers around the building. News reports said several people were injured, at least one seriously.
The opposition has challenges, too. The leftist Party of the Democratic Revolution has split into factions, and the National Action Party is rebuilding without a clear leader after losing its 12-year grip on the presidency.
Randal C. Archibold contributed reporting.
