Mexico's election: Calderón the campaigner THE candidates in Mexico's presidential election are legally forbidden to campaign until March 30th. But President Felipe Calderón, who is barred from running, is hard at it. Opponents accused him of breaking the electoral rules when, at a bankers" conference last month, he brandished a poll showing the candidate of his conservative National Action Party (PAN) just four points behind Enrique Peña Nieto, the front-runner from the centrist Institutional Revolutionary Party (PRI). Other polls say the gap is much wider. Leaks say that federal prosecutors are investigating three former governors of Tamaulipas, a northern border state where criminals and politicians rub shoulders. All three, who deny any wrongdoing, belong to the PRI. Last year the finance ministry exposed an accounting scandal in Coahuila, another PRI-run border state. That led to the resignation of Humberto Moreira, the PRI's president, who had been Coahuila's governor at the time of the alleged book-cooking. Few commentators have rushed to defend the integrity of the Tamaulipas three. One of them, Tomás Yarrington, is also accused by the United States Drug Enforcement Agency of receiving drug money (though the DEA has sometimes been hasty with such accusations). But the timing of the investigation, some of which relates to matters more than a decade ago, and the illegal leaking suggest that the aim is "to provoke a parallel trial by the media, to fuel the perception that the PRI and the narcos are inseparable," says Saúl López, a law professor at ITAM, a university. Mr Calderón's government is already seen as uneven-handed in its pursuit of corruption. In May 2009 federal prosecutors ordered the arrest of ten mayors (eight belonging to the opposition) and 18 other officials in Michoacán over their alleged drug links a few weeks before mid-term elections. All were later freed. The collapse last year of cases against former opposition mayors in Cancún and Tijuana was similarly embarrassing for the government. The opposition is now worried about the impartiality of election watchdogs. Last month the attorney-general's office replaced José Luis Vargas, the head of its electoral-crimes unit. Mr Vargas recently declined to annul an election for governor of Michoacán, which Mr Calderón's sister had narrowly lost to the PRI. Not only did the PAN protest about these kind of shenanigans when the PRI was in power until 2000, they also risk giving the opposition grounds to impugn the result if it loses on July 1st.