Mexico’s investigation into a former governor accused of taking drug money has raised suspicions of political meddling, coming soon before the presidential election, but may instead reflect the influence of the US on the country’s strategy against organized crime.

Last week, the anti-organized crime division of Mexico’s Justice Department — known as the PGR, for its initials in Spanish — searched properties belonging to Tomas Yarrington (pictured), former governor of Tamaulipas, and three businessmen connected to him. The group is being investigated for money laundering and other crimes stemming from straw purchases of several mansions. The properties are located in a number of cities around Tamaulipas, including Ciudad Victoria, the state capital, and Matamoros, which is across the border from Brownsville, Texas.

Yarrington, who held the state’s top post from 1999 through 2004, was one of three former Tamaulipas governors put under investigation by the PGR in January. His term in office coincided with the rise (and the fall) of Gulf Cartel boss Osiel Cardenas, as well as the emergence of the Zetas, an armed group founded by Cardenas and initially composed primarily of army deserters. While the suspected links between Tamaulipas politicians and drug traffickers go deeper than any single administration, Yarrington in particular has long been accused of links to organized crime, and his case appears to be further along than those of the other two former Tamaulipas governors.

Yarrington was once seen as a potential presidential candidate, and is connected to some of the most prominent members of the Institutional Revolutionary Party (PRI). However, the party suspended his membership last week, and Enrique Peña Nieto, PRI candidate and frontrunner for the July presidential elections, was obliged to distance himself from the now-disgraced politician amid rumors that he had been arrested.

With Peña some 20 points ahead of the candidate from President Felipe Calderon’s National Action Party (PAN), many suspect that political calculations could be driving the investigations of various prominent PRI figures. The arrest of PRI heavyweight and former Tijuana Mayor Jorge Hank Rhon last year, which eventually resulted in an embarrassing dismissal of all charges, was the first of these supposedly political arrests. The detention of retired General Tomas Angeles earlier this month was also attributed by some to his supposed links to the PRI. While there is no clear evidence of a political motivation, as with Angeles and Hank Rhon, the allegations against Yarrington were longstanding, and he has been out of office for eight years, so the timing is striking.

However, Yarrington’s investigation comes amid a redoubled crackdown on corruption under Attorney General Marisela Morales. The attorney general, who took up the post a little more than a year ago, first began a purge of her own department, announcing that some 1,500 PGR employees would be leaving their posts. She has targeted not only anonymous bureaucrats, but prominent political figures who were overlooked in previous anti-corruption efforts.

Mexico’s governors have long been immune to anti-corruption drives, despite often being linked to illegal activities. Mario Villanueva, a former governor of Quintana Roo, has spent time behind bars both in Mexico and the US (where he is today) thanks to his relationship with the Juarez Cartel in the 1990s, but, since his arrest in 2001, no comparable case had emerged until the investigation into Yarrington. The apparent lack of interest in governors’ wrongdoing is all the more important because of the enormous role they play in Mexican public life, far beyond that of their counterparts in the US.

Yarrington’s arrest also fits with the government’s increasing focus on the Zetas and regions where they dominate, like Tamaulipas. The Zetas, whose reputation as one of the bloodiest gangs in Mexico goes back more than a decade, have long been a target of state forces. However, thanks to a series of provocative acts of violence, including the killing of a US federal agent in February 2011 and the murder of hundreds of people in San Fernando, Tamaulipas, they were labeled as the government’s top enemy last summer.

The investigation into Yarrington is also evidence of the outsized influence of the US in guiding not only Mexico’s broader strategy on organized crime, but also, perhaps, the individual targets of government crackdowns. The latest flurry of interest into Yarrington came after the Department of Justice launched an investigation into the ex-governor’s real estate purchases north of the Rio Grande, in Texas. Meanwhile, Angeles and three other generals arrested in the same sweep had faced accusations from the US Drug Enforcement Administration (DEA). And as mentioned, the Mexican government singled out the Zetas, after years of notoriety, only after they incurred US wrath with the February 2011 killing of ICE agent Jaime Zapata.