It's very name is symbolic of the way many - both inside and outside the country - regard the political machine which completely dominated politics in Mexico for most of the 20th century. The Partido Revolucionario Institucional (Institutional Revolutionary Party), known commonly as "pree" from its initials, ruled Mexico for more than 70 years until it was thrown out of office in the election of 2000.
It had begun as a bright light to take Mexicans into a new world after their revolution a century ago and ruled for a time through a mixture of populism and patronage, but as the years passed added corruption and repression to its tool kit.
The beginning of the end of the PRI's stranglehold on Mexican politics began in the late 1980s when a candidate for its main rival, the Partido Acción Nacional (National Action Party), was elected governor of the state of Baja California. The next decade was marked by a string of troubles - most of them self-inflicted - for the traditional ruling party whose candidate for president lost to the PAN's Vicente Fox as the century drew to a close in 2000. Five years later, in a string of state election defeats, the PRI lost control of half of Mexico's 31 states, and a year later the party - now deeply divided - suffered its worst defeat in a presidential election. Its candidate came in a distant third to Felipe Calderón of the PAN.
Tomorrow, as Mexicans go to the polls once again to choose a new president, national Parliament and various state offices, the PRI is once again a force to contend with. In the three-month campaign which ended by law on Wednesday, the PRI's candidate - a telegenic, 45-year-old former governor of Mexico State, Enrique Peña Nieto, has come out ahead and appears likely to regain the presidency for his party. He has capitalised on the troubles of the outgoing government, which has taken on the murderous drug cartels in a campaign which has cost some 50,000 lives. He promises increased growth by way of a series of overhauls, particularly in the oil industry, which the party nationalised in 1938. The state oil company, Pemex, provides one-third of the government budget, but doesn't have enough left over for proper development and new exploration.
His main rival is Andrés Manuel López Obrador, who ran the government of the federal district (meaning he was essentially the mayor of Mexico City), from 2000 to 2005 before resigning to run for president in 2006. We remember him as the man who kicked up a great fuss for months because he believed the election should have gone to him instead of Felipe Calderón. Now he's leading a coalition of his Partido de la Revolución Democrática (Party of the Democratic Revolution), the Labour Party and an urban activist group. Trailing well behind is the PAN's candidate, Josefina Vázquez Mota, an economist who began her working career in family businesses and with various business organisations and conferences. She was also a journalist and author, as well as a member of Congress.
The comeback of the PRI is a remarkable achievement for a party that was riven by internal dissension and fighting after the defeat a dozen years ago. But it had been able to retain control of half of the country's state governorships and a reduced but still substantial representation in both houses of Congress. And this time there has been no infighting leading up to the presidential election. It claims it has learned from its mistakes and mustered the full resources of its mighty party machinery in support of Peña Nieto. Public opinion polls published as the campaign closed this week showed him with a double-digit lead over his rivals.
When the PAN came to power it raised hopes with its programme of opening up the economy and fostering the private sector. It has succeeded to some extent, and Mexico is projected to lead the rest of Latin America in economic growth. Unlike other countries in the region, Mexico does not rely on natural resources but rather on a dynamic manufacturing sector, which exports everything from television sets to automobiles. The big obstacle for Calderón's administration is the dire toll his war on the narco-traficantes has racked up. It was a bold move, as he could have looked the other way and bought apparent peace while the criminal element ate away at the nation's vital structures and economy.
Unfortunately, even though the power and influence of the drug lords is considerably weakened, his party is paying the price for the international reputation as a place of carnage and lawlessness.
Whoever emerges as the new president tomorrow faces some serious challenges in the country's structures. First of all, there is that drug war, which is still a monster to be tamed. Peña Nieto vows to focus his attention on reducing the toll the activities of the narco-thugs exact from the society. He has to groom the law enforcers into a professional cadre which can replace the army in a task it is not suited for and in which it contributes atrocities of its own. Then there's the wider need for opening up the judicial and law-enforcement system to make it fairer and more transparent. And while Mexico has weathered the global economic storm reasonably well, its growth has been rather sluggish, well below that of some other Latin American countries at two per cent a year. The PRI's candidate says he has a plan for that too - reversing his party's traditional protectionism of Pemex by opening it up to foreign investment, widening the tax base and freeing up the country's labour laws.
All these will require political reforms, which many people expected with the victory of the PAN a dozen years ago. Mexico's politicians, for example, are the highest paid in the region, leading to the impression that they are in office only to look after themselves. An important factor is a peculiarity of Mexican political life - the concept of "no re-election".
This goes back to a prominent figure in Mexican history, Porfirio Diaz, who was president for 35 years in the late 19th and early 20th centuries. Diaz, a military leader in the country's turbulent formative years, began his presidency with the promise of no re-election. He soon changed his mind and ran a regime which eventually became marked by political stagnation and repression. He was finally overthrown by the revolution of a century ago after he threw his political rival into prison and declared himself the winner of an eighth term in office.
The people who drew up the constitution of 1917 insisted that the president can run for only one six-year term, and those who serve as deputies and senators cannot succeed themselves, but have to wait out a term before they can run again. As a result, politicians don't face the pressure of facing the electorate again for their actions or lack thereof.
In spite of its difficulties, Mexico and its 113 million people are poised to move from the ranks of the developing, into those of the developed nations. We wait to see what contribution Peña Nieto will make in that direction, should he be, as expected, the people's choice in tomorrow's vote.