Tamaulipas Gov. Tomas Yarrington, left, holds hands with former Mexican President Vicente Fox, second from left, and two other Mexican border governors before riding toward Nuevo Laredo, Mexico on April 21, 2002. (RAUL LLAMAS/ASSOCIATED PRESS)

The political watchers are calling it the Yarrington Affair, and it is beginning to read just like a Robert Ludlum thriller, alive with conspiracy theories and hidden motives. There are drug cartels, luxury condos and the highest political stakes. But so far, there’s no Jason Bourne, no lone hero.

The story begins with a suave Mexican politician ensnared in a widening corruption investigation in the middle of a presidential election, as the ruling party panics about an impending loss of power.

Last week, the former governor of the northern border state of Tamaulipas, Tomas Yarrington, denied allegations that he took money from the Gulf and Zetas drug cartels and, through a spider’s web of co-conspirators and bagmen, bought real estate and built front companies in Texas and Mexico, assets that are being sought by U.S. and Mexican law enforcement.

“It is false that I took bribes, it is false that I protected criminals, it is false that I laundered money for the narcos,” said Yarrington, who is under investigation in Mexico and is named in civil proceedings in the United States but has not been charged with any crime.

Yarrington was an important leader — and now a symbol — of the Institutional Revolutionary Party, or PRI, whose telegenic standard-bearer, Enrique Peña Nieto, is the front-runner in the July 1 presidential election.

The PRI ruled Mexico for more than 70 years, a one-party, sometimes ruthless autocracy that gave with one hand but took with the other. The question that looms over this election: Does Peña Nieto represent the old PRI, notorious for bureaucratic corruption, crony capitalism and alleged pacts with drug smugglers, or the new PRI, modern, transparent, effective and (relatively) clean?

Peña Nieto, a former governor, is leading most polls by double digits, ahead of rivals Josefina Vazquez Mota of the ruling party and Andres Manuel Lopez Obrador of the left, who narrowly lost the 2006 presidential election to Felipe Calderon and maintains that it was stolen.

Yarrington says he is a victim of the dark arts, a political persecution orchestrated by supporters of Calderon’s National Action Party, or PAN, to hurt Peña Nieto and help Vazquez Mota by reminding voters, at this crucial juncture, what the PRI has represented.

Seeking to limit any damage, the PRI threw Yarrington out of the party last month.

Many here assume it is possible that Yarrington and other top officials in Tamaulipas are being pursued because there is solid evidence of ties to the powerful Gulf cartel and its allies-turned-vicious-foes the Zetas, who post videos of torture sessions, hang women’s bodies from bridges and dump the headless torsos of hundreds of victims on the streets in macabre displays of violence.

“The question we are asking ourselves is: What if both things are true at the same time? That the Tamaulipas government has been controlled by the narcos? And that the Calderon government is using this case, at this point in time, to hurt its rivals?” said Lorenzo Meyer, a political analyst and professor at the College of Mexico.

Peña Nieto’s challengers are certainly beating the drums.

“This is a rotten regime of corruption” that Peña Nieto and the PRI have supported, Lopez Obrador said.

Vazquez Mota promised that if she emerged victorious in the election, her administration would quickly throw in jail not only the Sinaloa cartel’s boss, Joaquin “El Chapo” Guzman, but also Yarrington. On Sunday night, at the second and last presidential debate, she waved a photograph of Yarrington sitting next to Peña Nieto in a car, as the two campaigned together.

‘It’s good press’

Mexican prosecutors are trying to freeze all bank accounts linked to Yarrington and recently began proceedings to seize 30 properties tied to the former governor, who served from 1999 until 2004.

In civil proceedings in the United States, witnesses for the Drug Enforcement Administration allege that Yarrington took bribes from the Gulf and Zetas cartels, and law enforcement is trying to seize a $450,000 property in South Padre Island in Texas and 46 acres of land near San Antonio — both bought by frontmen, according to court papers.

Yarrington’s attorney, Joel Androphy, told the Associated Press that his client has no connection to the Texas real estate and that the Calderon government is going after Yarrington to hurt the PRI. “It’s good press, and it’s for political reasons,” Androphy said.

Many observers agree that the timing of the Yarrington Affair raises eyebrows. “Everything that happens in Mexico during an election season has a political interpretation,” said Jose Antonio Crespo, a political analyst and expert on the drug war at the Center of Research and Teaching in Economics.

“These could be dirty tricks by Calderon, but the fact that it comes during a presidential campaign does not mean that Yarrington is innocent,” he said.

A case of overreach?

The idea that a governor along the Texas border might have been in the employ of the Zetas would be profoundly depressing amid a U.S.-backed drug war that has taken more than 50,000 lives during the Calderon administration and turned the northern Mexican states into a conflict zone so hot that many Mexicans fear it.

But it is also possible that the Calderon government is overreaching. It famously went after a dozen mayors and top officials in the western state of Michoacan — and had to drop every case. It also prosecuted the former mayors of Tijuana and Cancun, but both investigations ended without charges.

Now another investigation is brewing, with three Mexican generals accused of ties to drug cartels.

“All are ‘allegedly’ linked,” said Gerson Hernandez, an expert in political communications at the Autonomous National University of Mexico. “Yarrington’s case is the same. He is allegedly linked to organized crime. All are alleged murderers. Alleged criminals. Alleged somethings.”

Researcher Gabriela Martinez contributed to this report.