Now, Michoacán is once again a key testing ground in this fight. Federal forces detained nearly 30 officials there Tuesday, including 10 mayors, for their alleged ties to drug traffickers. It is the largest sweep among the political class since Mr. Calderon took office in late 2006.
When sending some 45,000 military troops and federal forces throughout Mexico to battle drug traffickers that have taken control of towns throughout the country, Calderon also promised to root out corruption that in many cases allows traffickers to rule without consequence. Police officers at all levels have been at the center of that effort. But the arrest of local officials is an unprecedented step that most analysts say is crucial to winning this fight.
"What is significant about this is that it sends a very clearly message that not even elected officials are above the law," says Armand Peschard-Sverdrup, a Mexico expert in Washington at the consulting firm Peschard-Sverdrup & Associates.
From village mayors to high-ranking state officials
The operation in Michoacán, which comes ahead of important mid-term elections in July, involved 200 federal agents who stormed into the state attorney general's office in Morelia, as well as mayors' offices and police stations across the state. Others arrested include a judge and a former state police chief, who serves as an aide to the state's governor, according to the federal attorney's office.
In a press conference, Michoacán Gov. Leonel Godoy pointed out that those detained hail from a variety of political parties.
The mayors arrested govern mainly in mountain towns across the region, where marijuana production is common and where methamphetamine laboratories have been found. The mayor of Uruapan, which received worldwide notoriety in 2006 when gunmen stormed into a club and threw five human heads onto the dance floor, was also among those arrested.
Calderon's administration has arrested police officials across the country – in some towns disbanding whole forces as the military temporarily takes over. Police have been given polygraph tests and investigated to see whether they live outside their means, which could indicate whether they are taking money from organized crime networks.
Mexicans weary of corruption
The president has moved toward an overhaul of the federal police forces, improved intelligence sharing at all levels, and has launched Operation Clean House last year to investigate ties between the government and organized crime. Among the results was the arrest of Noe Ramirez, a former head of anti-organized crime in the attorney general's office.
But arrests at the local level are considered crucial. In an interview in December, Edgardo Buscaglia, a visiting professor of law and economics at the Mexico Autonomous Institute of Technology, said that organized crime, which ranges from money laundering to human smuggling, affects 63 percent of all the nation's municipalities.
The arrests of mayors is likely to play well with the Mexican public, too, especially in towns that are in the control of drug traffickers and where locals have long-suspected the cover of their elected officials.
"It will be well-received by Mexican people who are tired of the level of insecurity and complicity," says Mr. Peschard-Sverdrup. "They are the politicians that impact the daily lives of people the most."