The two Mexicos exist side by side in this steamy port city built by wildcatters and stevedores: the good, modern, more prosperous Mexico and the really bad Mexico, where gun battles break out at the local T.G.I. Friday’s and kidnapping crews roam middle-class neighborhoods, snatching teenage girls.

Voters here have their lives on the line in Mexico’s presidential election Sunday, in a city a few hours’ drive south of Texas where the municipal police were so hopelessly corrupt that they had their weapons taken away and their duties transferred to convoys of masked soldiers deployed to stem outright panic after two former mayors were abducted.

The vote, many residents say, is the worst kind of choice, between candidates and parties they don’t especially like or trust.

In the most violent quarter of Mexico, it is a vote based less on hope and more on fear. “We can’t survive like this forever,” said Jose Luis Sanchez, a businessman who has had to lay off two-thirds of his workforce in the past 18 months and worries constantly about the safety of his children. “We have to have laws.”

In today’s Mexico, stability and lawlessness coexist. While some cities remain safe, including heavily guarded tourist zones such as Cancun and Los Cabos, Mexico’s northern border towns and other drug-trafficking hubs rank among the most murderous places in the world.

(By Laris Karklis/The Washington PostThe Washington Post/The Washington Post)

Mexicans seem just as divided about the state of their country. A survey this month by the independent polling firm Buendia & Laredo found that a majority think Mexico is “on the wrong track.” But many members of the country’s expanding middle class remain upbeat about their personal prospects, with 59 percent saying their lives had improved or remained the same since Felipe Calderon became president in 2006.

Calderon and his predecessor, Vicente Fox, from the conservative, pro-business National Action Party, or PAN, have given Mexico nearly 12 years of economic stability and slow but steady growth. The financial shocks and wild peso devaluations of the 1990s and early 2000s were replaced by low inflation, booming trade, aerospace and automobile manufacturing, and the kind of balanced budgets the U.S. Congress can only dream of.

But Tampico is one of the places where the dark, scary Mexico is devouring the other one. In the nearly six years since Calderon declared war on the country’s drug mafias, the surrounding northern border state of Tamaulipas has become a cartel battlefield and a horror show, the scene of beheadings, mass graves and naked corpses left dangling from bridges. The port of Tampico and the highways and border crossings of Tamaulipas represent ­billion-dollar drug-smuggling routes to the United States.

Which is one reason that voters here appear ready to break with the current order and turn away from the ruling PAN party and its standard-bearer, Josefina Vazquez Mota, who is running third in a field of three major candidates.

Holding a double-digit lead in most voter surveys is Enrique Peña Nieto, the fresh face of the old political dynasty called the Institutional Revolutionary Party, or PRI, which ran Mexico from 1929 until 2000 with a firm authoritarian blend of cronyism and corruption that Nobel winner Mario Vargas Llosa called “the perfect dictatorship.”

The reality of the PRI is as well known here as anywhere in Mexico. The state of Tamaulipas has been run by an unbroken chain of PRI governors for 83 years. Its past three governors have faced accusations of corruption and links to drug traffickers.

Tomas Yarrington, governor from 1999 to 2005, was named last month in U.S. court documents as an alleged money launderer for the fearsome Zetas cartel. The current governor, Egidio Torre Cantu, was elected only after his brother was assassinated in a highway ambush in the last weeks of the 2010 campaign.

Yet the polls show the PRI’s Peña Nieto headed toward a landslide here. Why? “People are not stupid. They perceive things the way they are,” said Guadalupe Correa-Cabrera, a professor at the University of Texas in the border city of Brownsville and an expert on Tamaulipas politics and organized crime.

“They know that state and local authorities from the PRI have been linked to organized crime. Tamaulipas has always been a kind of narco state. But the situation was calm. The narcos didn’t mess with us. But when Calderon declared war? Things became really bad, and this is what the people know,” Correa-Cabrera said.

‘Going back to zero’

The U.S. government, from President Obama to the Republican leadership in Congress, never misses an opportunity to praise Calderon for taking on the cartels, which earn billions running dope across the border to the world’s biggest drug market.

But here in Tamaulipas, voters see few benefits to the crackdown and say they are paying the price for a reckless, poorly planned strategy of military confrontation, undermined by corrupt or incompetent police, courts and judges.

Said one rancher who lives in Tampico but feared giving his name: “We know what’s going on. With the PRI, you have lots of dishonesty, lots of stealing, okay? But when I was driving to my ranch under the PRI, I didn’t see bodies without heads. Now I do. How many restaurants have closed? Stores, warehouses, businesses gone? The people in Tampico with any money have left or are leaving.”

Sanchez, the struggling local businessman, remains a fierce critic of the PRI but conceded that Peña Nieto’s party is organized and disciplined — “like a cult” — and capable of wielding the kind of authority that may be the only hope for bringing Mexico’s criminal mafias to heel.

“I don’t know what would be possible if the PRI used its power to achieve good,” Sanchez said. “But when you plant a mango tree, you can’t expect to get apples.”

He said that the PRI “has corruption in its DNA” and that bringing the party back in power would be a Faustian bargain for Mexico. “It’s the easy path, but in the long run, it’ll be more torturous. Like going back to zero,” he said.

Only zero may be better than what Tampico has now.

‘People are scared’

The city of 300,000 has become an abysmal place to do business. In the past year, Sanchez’s industrial safety equipment supply company has withered from 36 employees to 12 because his most important customers, oil workers, are too scared to drive out to the rural areas — Zeta country — where the wells are.

Sanchez this year closed a shop that had been opened by his grandfather in the 1930s. He carries no business cards, like many of his peers here, to protect his identity in case he’s kidnapped. His daughter has been carjacked at gunpoint. Close relatives and friends have been abducted.

“People here drive around without any documentation in their vehicles,” Tampico security official Graciela Tovar said. “Maybe they will steal your truck off the street. So what? Better that than having them get your documents and living with the fear that they’ll come to your house and kidnap you.”

Few people answer calls from phone numbers they don’t recognize. Fewer still were willing to speak with foreign journalists. “On the surface, things look normal, but they are not,” said Carlos Heredia, a scholar at Mexico City’s Center for Economic Research and Teaching who is from Tampico. “It’s a small city. Everybody in politics and business knows each other, and I can tell you people are scared.”

Heredia said voters in Tampico are responding to Peña Nieto’s promise to focus on the crimes that hurt ordinary Mexicans the most — kidnapping, extortion, robbery — rather than trying to stop the global narcotics trade. But Heredia and others ask: How can you confront these types of crimes without going after the large mafias that sponsor and profit from it?

Like other troubled regions of the country, Tampico appears to be near a breaking point. The area continues to attract robust amounts of foreign investment, with chemical company DuPont putting $500 million into a new plant near the port and South Korean steelmaker POSCO planning to invest $300 million to double production at its local facility.

But members of Tampico’s business community and middle class say the flight will continue — to Texas, or the safer cities of central Mexico — until order is restored.

“Imagine if we had better security conditions,” said Rolando Ramirez, president of the local business owners’ association. “The economy here could really take off.”