For more than seven decades under the unbroken rule of Mexico's Institutional Revolutionary Party (PRI), suspicions of corruption were common, but rarely was anything brought to light. But the victory three years ago of opposition President Vicente Fox moved Mexico from a one-party government to one where six parties hold congressional seats, and was hailed as a step forward for open government.
Yet in the past six weeks, videotapes of officials from two parties apparently accepting large amounts of cash, negotiating bribes, and gambling - followed by denials, accusations, and disappearances - have sullied that image. The revelations, which are airing nightly on the news, have reignited Mexicans' suspicions about the persistence of corruption in public life.
"Everyone thought things had changed, but they're finding out that Mexico's political system continues to decay," says political analyst Felipe Moreno.
None of Mexico's four largest parties has emerged unscathed. But the left-leaning Revolutionary Democratic Party (PRD), which has promoted an honest image that promised a break from the influence-peddling politics of Mexico's past, has been hit hardest of all. Sunday, a co-founder of the PRD, Cuauhtemoc Cardenas, resigned, citing his dissatisfaction with the party leadership's handling of the situation.
Just a month ago, thousands of Mexicans were rallying behind Andres Manuel Lopez Obrador, the PRD mayor of Mexico City. Mr. Lopez Obrador, who makes a point of modest living, even taking a pay cut, was the leading candidate to win the Mexican presidency in 2006.
Now he's tied for second in opinion polls, having fallen behind Santiago Creel, Mr. Fox's top minister and the National Action Party's (PAN) leading candidate. His decline is the apparent result of having nearly a dozen subordinates caught up in a bribery scandal that rivals a soap opera. One tape showed the city's top councilman and former personal secretary to Lopez Obrador taking $45,000 in cash from a businessman, who secretly recorded the transaction. No proof of corruption by the mayor has turned up.
Similar problems have dogged the PAN's ideological leader, Sen. Diego Fernandez de Cevallos, who soon could be indicted for conspiring with the same businessman - Argentine-born Carlos Ahumada, now a fugitive from the law - to release the tapes of PRD corruption to the media rather than report them to criminal authorities. And another PAN candidate for the presidency in 2006, first lady Marta Sahagun, is accused of using a nonprofit group she heads to promote her campaign.
The charismatic president of Mexico's fourth-largest political group, the Green Ecologist Party, also made an embarrassing appearance on tape (covertly made by party dissidents), negotiating a $2 million bribe for permits to build on protected lands. Federal and local law-enforcement groups have opened investigations into corruption and theft in the Green Party that may lead to its official disbandment.
The PRI has taken a hit as well. Amid an internal power struggle came the embarrassing news that former Mexican president Miguel de la Madrid of the PRI had just admitted to fixing the 1988 presidential elections.
The scandals have caused politicians in three of the nation's top four parties to resign or be pushed out in recent weeks, including four Mexico City officials, all PRD members. Four others, led by the city's former secretary of finance, Carlos Ponce, have disappeared and are wanted after a tape turned up showing Mr. Ponce gambling thousands of dollars of what may have been public funds in Las Vegas.
For most Mexicans, the rapid-fire blows of "videogate" have been a depressing wakeup call. "I guess putting all the videos into the public eye is a good thing for the country," said Francisco Trujillo, who lives east of Mexico City. "Now we know that all the politicians haven't been serving Mexico, they're being served by Mexico."
The latest polls show that public trust in a range of elected officials - including many who have had no involvement in the scandals - has crashed; not one managed a 50 percent favorable rating on honesty.
"The worst thing is that [from the point of view of today's politicians], the criminals aren't those that taped, nor those that robbed, nor those that took the money, but those that spoke up and brought to the videos to light," wrote Mexico City resident David Frid in a letter to the paper Reforma.