Voters in El Salvador will go to the polls on Sunday to choose a new president from two decidedly opposite ends of the political spectrum. Former guerrilla and current Vice President Salvador Sanchez Ceren, of the hard-line wing of the Farabundo Marti National Liberation Front (FMLN), is facing off against San Salvador Mayor Norman Quijano of the pro-U.S. opposition Nationalist Republican Alliance (ARENA) party.

As if the stakes were not high enough already - for the Salvadoran people and for U.S. interests in the region - the election is being complicated by the unhelpful role of a third-party candidate, Antonio Saca, the former president of the country who served under the ARENA banner from 2004 to 2009.

Once a favorite of the George W. Bush administration, Mr. Saca was subsequently expelled from ARENA in 2009 for his conspicuous corruption while in office. Today, many in El Salvador think he is running again as a part of an under-the-table agreement with the FMLN to split the opposition vote in exchange for immunity from corruption charges should the FMLN win the election.

Karl Marx once wrote that history repeats itself, first as tragedy, second as farce. Regional observers cannot help but notice the obvious parallels between what is happening in El Salvador today and what occurred in the Nicaraguan presidential election of 2006, which was undermined by a similarly corrupt pact that allowed the Sandinistas' Daniel Ortega to win office with 38 percent of the popular vote.

That deal involved another disgraced former president, Arnoldo Aleman, who financed a third-candidate to split the opposition against the Sandinistas in return for immunity for charges of widespread graft during his presidency. (In 2004, Transparency International named Aleman as one of the most corrupt leaders in recent history and estimated he looted his country of an estimated $100 million.)

According to ARENA official Ernesto Muyshdont, Mr. Saca is aping that model: "For us, it's quite clear. Here, the FMLN's strategy is to replicate what the Sandinistas did in Nicaragua, which is to make an alliance with a corrupt leader from the right in order to remain in power, guaranteeing that the latter's offenses remain in impunity in exchange."

Clearly, Mr. Saca has every motive to avoid judicial scrutiny of his time in office. According to an investigation by a Salvadoran newspaper, El Faro, during his presidency, Mr. Saca's personal wealth skyrocketed from around a half-million dollars to more than $10.5 million.

The U.S. Embassy, for one, noticed, as reflected in several diplomatic cables released by WikiLeaks. "Considerable evidence exists," reports one, " that the Saca administration pushed laws and selectively enforced regulations with specific intent to benefit Saca family interests.

Saca also accumulated conspicuous assets - including a mansion in San Salvador and large landholdings in La Union - that do not square with the investments and income he had prior to assuming the presidency."

If Antonio Saca was once a friend of the United States, he is not one today. His cynical, transparent machinations have unmasked him as another corrupt caudillo who has made common cause with those who would undermine El Salvador's democracy, prosperity and security.

Mr. Saca has no chance of winning the election; he is polling in the low teens. Meanwhile, Mr. Ceren and Mr. Quijano are running neck-and-neck in the low 30s. Any vote total less than 50 percent for the winner means the election goes to a second round between the two front-runners.

ARENA thinks that if Mr. Saca were not in the race, Mr. Quijano would win the election in the first round. ARENA supporters say the FMLN has to get to a second round, where it can open the funding spigot from Venezuela in a head-to-head match.

Beyond that, the election reflects the changing nature of the threats to democracy and rule of law in Central America. No longer is it just about ideology. Criminality and corruption - aided and abetted by drug trafficking - are posing a more lethal threat. As long as corrupt leaders are able to enjoy impunity for their crimes, the situation will only worsen.

Unfortunately, the Obama administration has failed to mount any effective policy to contend with the new threats. First, it should reassess its languid support for election-monitoring processes in the region, instead of just sloughing off the job to the Organization of American States.

The United States has as much stake as anyone in a clean election in El Salvador. Without purposeful scrutiny to demand transparency and accountability in electoral processes, the enemies of democracy will easily carry the day.

With Mr. Ortega in Nicaragua today talking about changing the constitution to allow for his unlimited re-election, the fact that he and Arnoldo Aleman got away with their corrupt pact is a tragedy for democracy and the rule of law in Nicaragua. If history is repeated in the same subversion of the democratic process in El Salvador, it would indeed be a farce.

Jose R. Cardenas was acting assistant administrator for Latin America at the U.S. Agency for International Development in the George W. Bush administration and is an associate with Vision Americas.