MEXICO CITY — President Enrique Peña Nieto has shown remarkable leadership in passing key reforms to reanimate the economy and further the development of Mexico. But now he must act quickly to re-establish his political credibility and limit damage to his moral standing. The present crisis requires it.

Thousands of young people have been marching in the streets of Mexico since the kidnapping and murder of 43 students (now confirmed by the DNA of a burned body) from a college in Ayotzinapa in the state of Guerrero. According to Mexico’s attorney general, the crime was committed by professional killers working for a narco- gang and under the orders of the former mayor of the town of Iguala, who was a member of the leftist Party of the Democratic Revolution (PRD). Although most of these criminals, including the mayor and his wife, have been arrested, the student protesters are blaming the Peña Nieto government of the centrist Institutional Revolutionary Party (PRI) and questioning its legitimacy. They are even demanding that the legally elected president resign from office.

Although most Mexicans may not support so extreme a demand as resignation, the popularity level of the president has sunk quite low, and not only because of the slow response to this atrocious crime. The suspicion of a conflict of interest over his wife’s partial purchase of a luxury mansion has further clouded the situation for Mr. Peña Nieto. Distrustful of government and fed up with the violence and insecurity unleashed by the drug cartels, Mexicans feel a profound moral and political resentment at a situation that those of us who struggled for the coming of democracy at the turn of the millennium never expected to confront. While there have been incidents of violence among the protesters, most of the demonstrations have been peaceful but intensely angry. And their anger is justified.

“No vale nada la vida, la vida no vale nada” (Worth nothing is life, life is worth nothing) goes a famous Mexican song whose subject is macho boastfulness but whose words sadly reflect the deadly realities in my country. There have been about 100,000 deaths from criminal violence in this new millennium. In the state of Tamaulipas on the northeastern border, civil authority is almost nonexistent, and journalists, bloggers and even tweeters are routinely assassinated. In Guerrero, more than a dozen criminal gangs are operating, and mayors and local police often collaborate with them. In entire areas of the states of Michoacán, Morelos and Mexico (a state adjacent to the capital), kidnappings, assaults and extortion are endemic. Ninety-eight percent of the crimes have gone unpunished. It is this near-total impunity that is the country’s foremost problem.