In just a few days, on Sunday 5 June, an election will take place that will have a significant influence on the western hemisphere. At the moment, it is too close to call. Most of official Washington has been relatively quiet, but there is no doubt that the Obama administration has a big stake in the outcome of this poll.

The election is in Peru, where left populist and former military officer Ollanta Humala is facing off against Keiko Fujimori, the daughter of Peru's former authoritarian ruler Alberto Fujimori, who was president from 1990-2000. Alberto Fujimori is in jail, serving a 25-year sentence for multiple political murders, kidnapping and corruption. Keiko has made it clear that she represents him and his administration, and has been surrounded by his associates and former officials of his government.

Fujimori was found to have had "individual criminal responsibility" for the murders and kidnappings. But his government was responsible for many more widespread murders and human rights abuses, including the forced sterilisation of tens of thousands of women, mostly indigenous.

Between the two candidates, whom do you think Washington would prefer?

If you guessed Keiko Fujimori, you guessed right. I spoke Monday night with Gustavo Gorriti in Lima, an award-winning Peruvian investigative journalist who was one of the people that Alberto Fujimori was convicted of kidnapping. "The US embassy strongly opposes Humala's candidacy," he said. Harvard professor of government Steven Levitsky, who has written extensively on Peru and is currently visiting professor at Pontificia Universidad Católica del Perú (PUCP), came to the same conclusion: "It's clear that the US embassy here sees Keiko as the least bad option," he told me from Lima on Tuesday.

Humala's opponents argue that Peru's democracy would be imperilled if he were elected, pointing to a military revolt that he led against Fujimori's authoritarian government. (He was later pardoned by the Peruvian Congress.) But his record is hardly comparable to the actual, proven crimes of Alberto Fujimori.

Humala is also accused of being an ally of Venezuela's President Hugo Chávez. He has distanced himself from Chávez, unlike in his 2006 campaign for the presidency. But all of this is just a rightwing media stunt. Chávez has been demonised throughout the hemispheric media, and so rightwing media monopolies have used him as a bogeyman in numerous elections for years, with varying degrees of success. Of course, Venezuela is also irrelevant to the Peruvian election because almost all governments in South America are "allies of Chávez". This is especially true of Brazil, Argentina, Bolivia, Ecuador and Uruguay, for example, all of whom have very close and collaborative relations with Venezuela.

As in many other elections in Latin America, rightwing domination of the media is key to successful scare tactics. "The majority of TV stations and newspapers have been actively working for Fujimori in this election," said Levitsky.

The thought of another Fujimori government is so frightening that a number of prominent conservative Peruvian politicians have decided to endorse Humala. Among these is the Nobel prize-winning novelist Mario Vargas Llosa, who hates the Latin American left as much as anyone. Humala has also been endorsed by Alejandro Toledo, the former Peruvian president and contender in the first round of this election.

So why would Washington want Fujimori? The answer is quite simple: it's about Washington's waning influence and power in its former "backyard" of Latin America. In South America, there are now left-of-centre governments in Argentina, Brazil, Venezuela, Ecuador, Bolivia, Uruguay and Paraguay. These governments have a common position on most hemispheric issues (and sometimes, other international issues, such as the Middle East), and it often differs from that of Washington.

For example, when the Honduran military overthrew the country's elected left-of-centre president, Manuel Zelaya, in 2009, and the Obama administration sought to legitimise the coup government through elections that other governments would not recognise, it was Washington's few rightwing allies that first broke ranks with the rest of South America.

Prior to last August, the only governments in South America that Washington could count as allies were Chile, Peru and Colombia. But Colombia under President Manuel Santos is no longer a reliable ally, and currently has very good co-operative relations with Venezuela. If Humala wins, there is little doubt that he will join the rest of South America on most issues of concern to Washington. The same cannot be said of Keiko Fujimori.

And that is why Washington is worried about this election.