SANTIAGO, Chile — When democracy returned to Chile nearly two decades ago after the dictatorship of Gen. Augusto Pinochet, rivals on the political left and center realized they needed to work together to make sure the bad old days of political polarization didn't return.
That's when four parties formed what's become the main political force here over the past 18 years, the Concertacion coalition, which has given the citizens of this nation of 16.3 million the political stability and consensus it desperately needed.
The coalition appears to be falling apart now, however, more than halfway through its fourth straight government. The common wisdom is that the administration of President Michelle Bachelet could be the last one of the Concertacion.
A poll by the nonprofit Public Studies Center released last week showed businessman Sebastian Pinera, the presumptive presidential candidate of the conservative Alliance for Chile coalition, handily beating any of the Concertacion's four main candidates in next year's presidential elections.
Former President Ricardo Lagos, whom Bachelet succeeded, came closest to Pinera, receiving 36 percent of the support to Pinera's 45 percent in a two-person contest.
The poll was another sign of the coalition's demise, with fierce bickering among Concertacion's parties leading even its leaders to admit that next year's elections will be their toughest yet.
If the predictions come true, the political right could govern Chile for the first time since Pinochet.
"We're in a difficult period," said Sen. Hosain Sabag of the centrist Christian Democrat party, which belongs to the Concertacion. "We have less unity than we did just two years ago. And after nearly 20 years, we're talking more about points that divide us than unify us."
Leftist members of the coalition delivered an even bleaker diagnosis while criticizing the moderate, market-friendly policies that Concertacion governments have followed. The other three parties in the coalition are the Socialists, the Party for Democracy and the Radical Social Democrat Party, all of them left-leaning.
"We are very close to losing the elections," said Sen. Alejandro Navarro of Bachelet's and Lagos' Socialist Party. "The biggest critics are in the Concertacion, but the leaders don't want to hear about it."
The coalition's biggest challenge has been finding a purpose in a post-Pinochet, democratic Chile that can keep it united, political analyst Carlos Huneeus said. The dissolution, in fact, already has begun, with the coalition planning to run two slates of candidates in October's municipal elections.
The coalition first formed in 1988 to urge a "no" vote on a nationwide plebiscite deciding whether Pinochet should stay in power for another eight years.
Pinochet lost that vote, and the first Concertacion government, of President Patricio Aylwin, came into power two years later. Aylwin faced the tough task of overseeing the transition from authoritarian to democratic rule while ensuring that economic growth continued.
By that measure, the coalition has succeeded. Chile claims one of Latin America's healthiest democracies, and its economy has grown by about 5 percent a year ever since.
In fact, the coalition may be a victim of its own success. The waning influence of Pinochet took some of the fight out of the Concertacion, and the former dictator's death in December 2006 may have been the beginning of the end, Huneeus said.
"Pinochet is gone, the human-rights values battle has been won and democracy is consolidated," he said. "The reasons for the Concertacion's existence just don't exist anymore."
The coalition also has been hurt by the Bachelet government's missteps, which drove her approval rating down to around 35 percent a year ago. She took the biggest hit when her government flubbed the 2006 launch of a new public-transit system, which overcrowded buses and lengthened transit times in the capital of Santiago.
The president's approval rating rose to 51 percent in last week's poll, but the damage already may have been done, Huneeus said.
"The political cost of the transit system chaos was terrible," he said. "It showed that the government was fundamentally incapable of dealing with the problem."
Longtime Concertacion voter Rodrigo Casanova, a university professor, said he planned to turn in a blank ballot next year, complaining that the Concertacion had lost touch with ordinary Chileans. He was particularly unhappy with what he said was the coalition's failure to strengthen public education, an issue that's sparked massive street protests.
"Twenty years later, all we have is a kind of agreement among the leaders of the parties to not lose the next election," Casanova said. "They don't listen to the people, to most of Chile."
Opposition leaders have jumped on Bachelet's mistakes and have promised to run a more receptive and professional government if the Alliance for Chile wins.
"I think the Concertacion has reached the end of its road," said Sen. Hernan Larrain, the former head of the conservative Independent Democrat Union party. "The unifying factor of the government is gone, and the Concertacion is not part of the political reality of the moment."
A switch in government next year wouldn't usher in the kind of political U-turn that the country took when the ultraconservative Pinochet seized power in a 1973 coup that ousted Socialist President Salvador Allende.
Pinera probably would follow the same macroeconomic policies of open markets and fiscal prudence that the Concertacion has hewed to and would tinker only with education, public safety and other domestic programs.
He's also distanced himself from the Pinochet legacy, making it clear that he voted against extending the dictator's rule in 1988.
Politicians on both sides said that political stability, as opposed to the abrupt shifts seen in other Latin American countries, might be remembered as the Concertacion's greatest achievement in its nearly two decades in power.