MEXICO CITY -- There's an old story about a visit to the presidential palace here by the revolutionary Emiliano Zapata. Asked to try the presidential chair, he declined and later said, "We should have burned it to put an end to ambition."
In the 80 or so years since Zapata's suggestion, Mexicans of democratic inclination have been trying to "burn the chair." To Zapata and others it symbolized the abuse of power and unrestrained ambition.
About the only progress achieved to circumscribe the authority of the Mexican president was the limit put into the 1917 constitution making his term of office six years, with no re-election.
Now, the presidential candidate of the Institutional Revolutionary Party, PRI, which has ruled continuously longer than any party in the world, promises, if not to burn the very chair he's seeking to occupy, at least to cut it down a peg or two.
Ernesto Zedillo Ponce de Leon said he would, if elected, abolish one of the most nondemocratic conventions within the PRI: the president's authority to name his successor.
"I want to emphasize," he said, "that I am resolved not to intervene in any manner in the selection of PRI candidates . . . from mayors to the president of the republic."
This custom he has promised to forgo is known as the "dedazo" -- the tapping of the successor with the finger. As it is such a huge component of the Mexican president's political armory, it is reasonable to ask if Mr. Zedillo really meant it.
He did, insisted Jose Angel Gurria, a PRI mandarin and campaign official. "That was the line that brought every one of the party faithful to their feet," he said.
Outside the ranks of the PRI, Mexicans appear underwhelmed by this grand gesture to democracy. Why? Mr. Gurria said it is because "the constitutional implications are so far reaching they will take the Mexican public some time to digest."
It is also likely many people don't believe it.
"In this country we have a very high production of promises," said Salvador Garcia Linan, who speaks for Mexico's owners of small- and medium-sized businesses. "Maybe he is feeling his campaign is not going well."
Diego Fernandez de Cevallos, the candidate for the opposition National Action Party, said dismissively that if Mr. Zedillo really feels the "dedazo" is such a bad thing, he ought to resign his candidacy.
"He's a product of this practice," Mr. Fernandez pointed out.
Mexico is a republic similar to the United States in that it has a formal division of powers -- an executive, legislative body and judiciary. But virtually all authority resides in the person of the president. He dominates the legislature, and no court has ever overturned one of the government's initiatives.
The "dedazo" is one expression of the president's authority. It is a "tradition, an unwritten law," said Armando Ayala Anguiano, the director of Contenido, a political magazine and digest.
Mr. Ayala says he does not think it is such an insidious practice today as it was some years ago when the PRI's domination of Mexico was nearly as thorough as the Communist Party's was over the former Soviet Union.
"Their way is that the president does it. I think it is fair," he said.
The "dedazo" was born in 1929 with the founding of the National Revolutionary Party, which evolved into the PRI, as a device for working around the constitutional ban on presidential re-election.
"It is an extension of the mandate, through another person," said Homero Aridjis, a writer and environmentalist.
But to Mr. Aridjis, it facilitates the continuation of the political corruption for which Mexico is so frequently faulted. The "rascals" are never thrown out. It discourages the development of new ideas. It inhibits the rise to positions of influence any people other than yes men and political nepotists.
"We have men in jobs in the government who were put there by presidents in the '70s," said Mr. Aridjis. "They are still there."
This kind of unhealthy continuity, he added, "also allows them to cover up their bad deeds, to cover their tracks. It is a long chain of complicity."