AT LUNCHTIME on Sunday November 2nd a group of students, some of them masked, “liberated” the toll booths on the motorway connecting Mexico City and the nearby city of Toluca. Your columnist, along with other queuing motorists, was peremptorily ordered to make a “voluntary contribution in solidarity with Ayotzinapa”. Neither motorway staff nor police were anywhere to be seen.

Daily protests, some as anarchic as that one and some massive, continue six weeks after Mexico was horrified by the disappearance of 43 trainee teachers from a college in Ayotzinapa, in the southern Mexican state of Guerrero, and the killing of six other people. The hijacked buses in which the students were travelling were intercepted by local police in Iguala, a nearby town, on the orders of its mayor, José Luis Abarca, and his wife, who are alleged to be leaders of a drug mafia and were arrested this week.

Mexico has grown used to violence since the ex-president, Felipe Calderón, declared war on drug gangs in 2006. In the maelstrom Mr Calderón unleashed, some 22,000 people have disappeared, many of them officially said to be criminals. But the fate of the Ayotzinapa students caused outrage on a scale not seen for decades, for three reasons.

First, the missing students are not anonymous victims. As Héctor Aguilar Camín, a writer and sociologist, points out, “22,000 disappeared is a statistic; 43 with names and families is a human-rights crisis.” Second, although the Ayotzinapa students had a history of lawless protests and possible links with a criminal gang, this was no settling of scores among drug traffickers. Rather, their apparent executioner (assuming they are dead) was the local state.

The third reason for outrage is that this human-rights crisis has left the government of Enrique Peña Nieto, Mr Calderón’s successor, seemingly paralysed—as absent as those toll-booth staff. Mr Peña dispatched federal police to Iguala; they have disarmed the local police in 17 nearby towns. But extraordinarily, he has yet to go there himself; a month passed before he met the grieving families.

In almost two years in office Mr Peña, of the centrist Institutional Revolutionary Party (PRI), has pushed through a radical programme of structural reform of Mexico’s hidebound economy. With economic growth starting to tick up after a weak spell, officials were in bullish mood. In securing a pact with the opposition to enact his economic reforms, Mr Peña showed himself to be a skilled political tactician. In several meetings with him, Bello has been impressed by the president’s political discipline—he and his senior officials always stick rigorously to the script.

Events have suddenly torn up that script, and the government finds itself facing a radically different political agenda. This starts with security, justice and the rule of law—issues that Mr Peña had sought to play down. His security policy stressed the role of state police forces. Yet Mexico’s 32 states include several failed ones, such as Guerrero. The overlap between politics and organised crime in many parts of the country is an open secret. Guerrero’s governor, Ángel Aguirre, a PRI stalwart before he switched to the left-of-centre opposition, has resigned over Iguala. He is alleged to have received money from the Abarcas, though he denies this. If he is to regain the initiative, Mr Peña will have to bring to justice political bosses known to be corrupt.

“We have to rethink, about the police and about access to justice,” says a senior official. “Structural changes” are needed, he adds, but they should not be rushed in response to media or social pressure. The government seems to think that if it resolves the Iguala case, pressure will ease. It may be underestimating the depth of public concern over security. This week, in a belated reaction to Iguala, the president urged the opposition to join him in a pact for the rule of law. To critics, this seems an evasion of responsibility.

Mr Peña governs through a small group of bright young technocrats, with old-time PRI stalwarts in security jobs. Though it is not in the president’s nature to go outside his coterie, his government would be boosted by a more substantial figure as interior minister, with the freedom to act. The obvious candidate is Manlio Fabio Beltrones, a leader of the PRI in Congress.

If he can react to events, change strategy and command the new political agenda, Mr Peña will have shown himself a far more substantial politician than he now looks. Respond too slowly, and he may lose the initiative for his remaining four years in office—and the credibility he needs to pursue his economic reforms.