The Nigerian Supreme Court has refused to terminate a lawsuit seeking to nullify the April 21 election of President Umaru Yar'Adua.
Nigeria's electoral commission had petitioned the court to dismiss the lawsuit filed by former vice president and presidential candidate Atiku Abubakar.
But in its ruling Wednesday, the court rejected the request, saying the commission's application was "incompetent."
Both local and international observers described Nigeria's April elections as deeply flawed due to widespread instances of fraud, intimidation and disorganization.
Abubakar, who ran on the ticket of the opposition Action Congress Party, finished second in the voting.
The electoral commission had initally asked Nigeria's Court of Appeal to throw out Abubakar's lawsuit. That court also rejected the petition.
In an interview with VOA's English to Africa service, an attorney for Abubakar, John Odubela, described Wednesday's court ruling as a victory, and said there is still a chance the presidential election might be annulled.
Nigerian courts have already overturned the results of five state governor elections conducted in April.