(CNN) -- Unable to defeat their political rival at the ballot box, some in the Venezuelan opposition are resorting to a tactic familiar to Americans: questioning the birthplace of the president.
In the United States, the so-called "birther" movement disputed President Barack Obama's legitimacy, claiming that he was born in Africa and therefore is ineligible for the highest office. Even when Obama's birth certificate was made public, some called it a forgery.
No birth certificate has been produced for Venezuelan President Nicolas Maduro.
Rumors of Maduro's birthplace surfaced before he was elected in April, but in recent weeks they have gained new life.
In the Venezuelan version of the birther movement, its proponents say Maduro was born in neighboring Colombia and is either a Colombian citizen or a dual citizen, either of which would make him ineligible to be president.
The leaders of the movement have taken their complaint to Venezuela's Supreme Court, to Colombian authorities and even to the European Union.
The claim is controversial in Venezuela.
Maduro's supporters ignore the question as nonsense.
The president has not addressed the question directly, but on several occasions said during speeches that he was born in Caracas. The Venezuelan government did not immediately respond to CNN's calls for comment.
The movement has gained the support of some opposition parties, which have asked the president to release a copy of his birth certificate.
"This is an international problem," Pablo Medina, a member of the opposition Patriotic Assembly, told CNN en Español.
Medina presented a letter to the European Union asking them to scrutinize Maduro's nationality and take a position on the matter.
He went to the European Union because other governments "should know that any contracts or any agreements that they sign with Nicolas Maduro, a Colombian citizen, are invalid, illegal, null and void."
This week, three lawyers asked the country's highest court to order Maduro to reveal where he was born, and what his parents' nationality is.
The birthers in the United States are considered a fringe group, and it's unclear how seriously Venezuelans consider the accusations against Maduro.
The theory that Maduro is not eligible to be president is welcomed by some Venezuelans who see it as a sliver of hope to unseat him. Maduro, the hand-picked successor of the late Hugo Chavez, narrowly won the election. Venezuela remains a polarized country, and there is a feeling that some factions will latch on to any tactic to remove Maduro from power.
Others ignore the issue altogether, or look at it with curiosity.
"I sincerely regret these rotten, ill-intentioned campaigns, which make us think about what would have happened if this country was in the hands of people who only act to destroy the dignity and reputation of others," wrote pro-Maduro columnist Casto Gil Rivera in the pro-government newspaper Correo del Orinoco.
Rivera wrote that he has known Maduro since he was a child -- in Caracas.
The fact that Maduro's birth record has not been located in either Venezuela or Colombia allows the doubts to persist.
According to Maduro's official biography, he was born in Caracas in 1962. During a speech in Italy in June, Maduro named a specific Caracas neighborhood as his birthplace as he recounted an anecdote about his childhood. He described it as a middle-class neighborhood and spoke of a memory he has of that place when he was 8 or 9.
Medina says his group has sought Maduro's birth record in the place where he says he was born, but found nothing.
To him, that is evidence that the president is not Venezuelan.
But no birth records for Maduro have turned up in Colombia, either.
A Colombian newspaper and radio outlet investigated allegations that the president's has Colombian roots in Cucuta, a town on the border with Venezuela, and found residents who had memories of Maduro as a child there.
However, both media investigations turned up no evidence that Maduro was born in Colombia. There is no record of anyone with that name having been born in Cucuta, RCN Radio reported.
So far, Venezuela's birther movement also has found no evidence to back their claims, much like their American counterparts. But, in another similarity, they stubbornly refuse to back down.
Asked whether he had any concerns about risking the credibility of the opposition by linking it to a birther claim, Medina said he is certain that he is right.
He said he was not aware of the way the birther movement is viewed in the United States.
Journalist Osmary Hernandez contributed to this report from Venezuela.