MEXICO CITY — All three of Mexico's main presidential candidates repeat the word "change" like a mantra — even the one from the party that has been in power since 1929. But as next month's elections approach, many analysts believe things will likely stay the same.

If an opposition party candidate wins, the most obvious change would be the end of the rule of the Institutional Revolutionary Party, or PRI, which has held the presidency since it was created in 1929.

But when it comes to specific issues, like the economy, rebels in Chiapas state, Mexico's fight against drug smuggling, what difference will it make who ends up claiming the presidency on Dec. 1?

Many analysts say very little.

There may be some changes on issues of democracy and the economy, but "things are likely to stay pretty much on course," said Eric Olson, senior associate for Mexico for the Washington Office on Latin America, an independent research and advocacy group.

Of the three top candidates, the one most likely to offer a different economic proposal is Cuauhtemoc Cardenas of the center-left Democratic Revolution Party.

He has called for renegotiating the North American Free Trade Agreement, greater investment in the state oil monopoly and increased subsidies for farmers and local contractors.

But Cardenas, who ran unsuccessfully for president in 1988 and 1994, is running a distant third in the polls.

Running neck-and-neck are the PRI's Francisco Labastida and Vicente Fox of the center-right National Action Party. Many analysts say they aren't all that different on many issues.

Labastida has accused Fox of planning to privatize the state-owned oil company, Pemex, but Fox has vociferously denied it — though Olson notes that both might try to bring more private investment into secondary parts of the oil industry.

"Vicente Fox would not be elected and then turn the entire economic model upside down on its head," said M. Delal Baer, a Mexico specialist at the Center for Strategic and International Studies in Washington. "He wouldn't revoke NAFTA, he would probably continue privatizations — and so would Labastida."

A major theme of Fox's campaign has been his promise to root out chronic government corruption that he says is a result of the PRI's uninterrupted run in office.

Labastida, who has championed himself as a representative of a "new" cleaner, more modern PRI, also has offered a detailed written proposal to stem the tide of corruption.

Both also have proposed professionalizing the police and paying them better salaries to better insulate them from the temptation of corruption.

The difference, says syndicated columnist and television commentator Sergio Sarmiento, is that Fox doesn't come from the traditional PRI establishment.

"He doesn't have to repay favors in any way. This would allow a major reform of the state structure," he said.

Fox has indeed proposed a major reform: the decentralization of power, shifting more decision-making power and revenue control to the states.

Labastida has said he would reinvent the formulas by which states receive federal funds, giving more money, for example, to sprawling Mexico state, and less to the superpopulated capital.

As far as drug trafficking is concerned, Baer believes both Fox and Labastida will be "pretty tough." But Sarmiento doesn't think either candidate would make much of a dent.

"You're really fighting against a market that generates a flow of drugs from Latin America into the U.S., and the market fundamentals are not going to change just because there's a new president," he said.

In Chiapas, where the PRI has more vested interests, Fox could perhaps bring a more flexible stance in negotiations. But the Zapatista rebels who waged a brief rebellion in 1994 for greater Indian rights are unlikely to want the kind of agreement that could be offered by either government.

Whatever promises they make, Fox and Labastida would face substantial opposition in the Congress, analysts said. Fox's party would certainly not have a majority in Congress, and Labastida's would be slim at best. And the legislature has been fighting hard to assert greater independence from the presidency.

And even if both candidates enter office armed with the best intentions to fulfill their promises, the experiences of both PRI President Ernesto Zedillo and the Democratic Revolution Party-run government in Mexico City "prove that for as much will as there is for change, reality is very stubborn," said Soledad Loaeza, a Colegio de Mexico researcher and expert on the National Action Party.

Immediate change is unlikely regardless of who becomes president, but if the opposition were to win, "there would be a dramatic change in the political structure," said political analyst Jose Antonio Crespo.

"The advantage would be that with a political structure that allows us to confront these problems in a civilized and fairer manner, the country can move forward," Crespo said.