Mexican political commentators call them "the three Charlies," describing them as the money and power behind the upstart presidential primary campaign of a former state governor named Roberto Madrazo.

Politically speaking, it is a lethal charge. The three are among Mexico's most unpopular characters: disgraced former president Carlos Salinas de Gortari; a jailed banker, Carlos Cabal Peniche; and millionaire political godfather Carlos Hank Gonzalez, whose family U.S. officials accuse--despite his strenuous denials--of assisting Mexican drug trafficking and money laundering operations.

This is the most open and democratic presidential campaign in Mexican history, but the trio's true role in it may never be known. Mexico is gradually moving toward U.S.-style elections after 70 years of rule by the Institutional Revolutionary Party (PRI), but it does not have tough disclosure laws to unmask the money men behind increasingly high-cost campaigns.

As a result, while the sitting president no longer picks the PRI candidate behind closed doors and Mexico's first genuine presidential primary will be held this Sunday, Mexican voters may never know what power brokers and vested interests funded the PRI's primary candidates--or, for that matter, the nominees of other parties.

Mexico's presidential sweepstakes began in earnest last winter, but campaign finance reports do not have to be filed with the Federal Electoral Institute until two months after the July 2000 general election. Even those reports will not be made public until March 2001, four months after the new president takes office, and finance reports for the Nov. 7 PRI primary need never be released.

"No one has to disclose anything at all," said legislator Santiago Creel, a member of the center-right National Action Party (PAN) and a leading reformist in Mexico's federal congress who is seeking his party's nomination for mayor of Mexico City.

As is the case elsewhere, Mexican candidates hold fund-raisers and pass the hat for contributions from the public, but big money and connections have long played decisive roles in elections. The issue is drawing particular attention here now, eight months before election day, because one of the most important milestones of the campaign is the PRI primary.

The other two main parties, the PAN and the center-left Democratic Revolutionary Party (PRD), already have chosen their candidates in limited, pro forma primaries funded by similarly opaque financing. But it is the PRI primary, with its national scope and genuine competition, that has generated big advertising, big money--and big questions.

Previously, after a president selected the PRI candidate, the ruling party simply tapped the national treasury to bankroll its campaigns. Few people donated money to opposition parties, since they were virtually certain to lose.

"Before, you played by the rules of the time and supported the PRI," said a Mexico City political consultant who asked not to be identified. But more recently, because of unprecedented opposition victories in state elections, "the private sector has learned that they lose if they chose wrong, so in 2000 they want to play it safe and give money to all three" of the major parties' candidates, "but without the others knowing."

It is not just Madrazo's campaign that has drawn critical review. His main opponent for the PRI nomination, former interior minister Francisco Labastida Ochoa, is considered by most people to be the official candidate and is alleged to be receiving huge amounts of support--especially in-kind contributions, such as food and vehicles for campaigners--from government and party loyalists, despite rules barring government aid.

Labastida has denied the allegations, which, like the charges against Madrazo, are impossible to substantiate or refute without public access to reports on campaign spending and fund-raising.

Vicente Fox, the PAN's presidential candidate, has prepared for the general campaign by gathering millions of dollars--all legal donations to a group called the Friends of Fox--from businessmen around the country, especially wealthy executives in Monterrey, the northern industrial capital.

Aides to Fox, the former president of Coca-Cola in Mexico, say his donor group spent about $11 million in the last 18 months. The group is not required to file reports with federal election authorities on how the money was raised or spent, although Fox campaign officials said that about three-quarters of it went to television and radio ads.

The other main candidate, the PRD's Cuauhtemoc Cardenas, does not appear to have a major money source other than his party. Cardenas, who lost presidential bids in 1988 and 1994, draws most of his support from the urban poor and people loyal to the memory of his father, who was considered one of Mexico's greatest presidents.

On the surface, some of Mexico's new campaign finance laws are strict, designed to reduce influence buying and give opposition parties a fair shake in getting their message out. About three-quarters of all campaign spending appears to go for advertising. Public financing is doled out according to party showings in the previous election, and federal law prohibits political donations by religious groups, Mexican businesses and all foreign businesses, individuals and organizations.

But the limits permit private gifts up to about $76,500, while loopholes make other laws meaningless. Anyone can give to a nonprofit interest group, for instance, and that group can pass the money to a political contender without having to disclose the source, according to officials with the Federal Electoral Institute.

There are no federal laws restricting campaign fund-raising or spending until the presidential campaign officially starts on Jan. 15, meaning candidates and groups that support them can raise and spend as much as they like before then without having to report it. Once the campaign season starts, a candidate and his party cannot spend more than $53 million on the presidential race.

But the most immediate concerns about reporting requirements center on the ruling party primary, which is not subject to any laws. The PRI, to ensure fairness among the four candidates vying for its nomination, mandated that they could not spend more than $5.7 million each on their primary campaigns. But there are virtually no rules restricting who can contribute to a campaign or how much anyone can give, and the campaigns of both leading candidates have accused the other of wild overspending.

"We'll never know how much they spent and where the money came from," said Francisco Javier Santillan, a top official in the campaign of Humberto Roque Villanueva, another PRI presidential candidate who is far behind in primary preference polls. "We'll never be sure that the information the party gives us is the truth."

Madrazo--who was accused of spending $70 million to win his 1994 election as governor of the oil-rich southern state of Tabasco, more than 60 times the legal limit--denied in an interview that he is spending lavishly on his presidential bid or that any of his money came from the three Charlies. But allegations in two recent books, as well as articles in newspapers across the political spectrum, PRI officials, Labastida campaign officials and independent political observers say Madrazo's prolific campaign spending can only be explained by their backing. Madrazo acknowledged past ties to the men but said that in Mexico "everybody's guilty until proven innocent."

"A culture of suspicion has been created," he complained. "What started the culture? Doubt, uncertainty, distrust until the moment arrived when you cannot distinguish the truth from the lies."

Labastida has never effectively countered the conventional wisdom that he has the backing of the PRI's powerful machine, which has mobilized voter blocs--from labor to peasants to housewives--at every level of Mexican society for the last 70 years.

Labastida's campaign said it is limiting donations to about $1,600 per person, but he is the only candidate with a voluntary cap. Campaign officials said they will release a full list of more than 8,000 donors on their Web site before the primary.

President Ernesto Zedillo has repeatedly denied that any candidate is his favorite, but most political observers see numerous signs that Labastida is the party hierarchy's choice. And most critically, they said, the PRI machine knows how to read sign language and deliver the vote, whether or not someone from above orders it to.

Researcher Garance Burke contributed to this report.

CAPTION: Carlos Salinas de Gortari, left, Carlos Cabal Peniche, center, and Carlos Hank Gonzalez, known as the "three Charlies," are said to have financed the presidential primary campaign of former Tabasco state governor Roberto Madrazo.