Cardinal Anthony Olubunmi Okogie, retired archbishop of Lagos, urged candidates to "publish their manifestoes and defend them."
"They should be bold to say this is what they will do when they get there. It is through this that the electorate will be convinced that such candidates will be able to perform on assumption of office,'' Okogie said.
The cardinal expressed fear that violence and bloodshed would erupt if the candidates do not keep in check comments about their opponents and their supporters.
"It's already happening, as you can see, that the atmosphere is tensed. I am praying seriously, I am begging God to avert it," he said.
''Look at the reports and advertorials in the newspapers. Instead of the candidates addressing the issues, the campaign is nothing but abuses, unearthing the past, disgracing themselves," he said.
Polls suggest a close race between President Goodluck Jonathan and former military ruler Muhammadu Buhari, who lost to Jonathan in 2011.
Nigeria has been beset by government corruption, a flagging economy despite immense oil wealth and the Boko Haram insurgency, which nongovernmental organizations estimate has forced up to 1.5 million people from their homes and claimed 11,000 lives.
Okogie challenged the candidates to explain how they will tackle the country's declining standard of education, unemployment, rising insecurity, poor electricity service, youth restiveness and kidnapping and hostage-taking.
"If we really want to keep Nigeria one as it should be, we should see one another as brothers and sisters. That's the correct and proper thing to do," he said.
The cardinal urged candidates to explain how they would partner with the international community to strengthen the Nigerian armed forces and offer plans to rescue more than 200 female students abducted in April.
He also warned candidates to guard against having political "godfathers" who would hinder them from fulfilling their campaign promises and suggested that corruption could end by reducing salaries for public officials.
"Then you will see that there will be few, sincere and honest people aspiring to political offices as against those jostling to milk the national cake,'' he said.
In Washington, the U.S. Commission on International Religious Freedom warned of the potential for religiously motivated violence around the election.
"Every effort needs to be undertaken to ensure peaceful elections and prevent the use of religion to stir up more violence," said a Feb. 2 statement from Katrina Lantos Swett, chairwoman of the commission. "The events leading up to and immediately following Feb. 14 are crucial to Nigeria's long-term stability and status as a multireligious and multiethnic society."