ABUJA, Nigeria - The minarets of the national mosque and the tower of the main cathedral soar to equal heights over Nigeria's capital. Religious leaders engineered the parity to promote unity amid sectarian violence unleashed at the end of military rule in 1999.

Just as deliberately, after eight years of rule by an elected southern Christian, all the main political parties have nominated northern Muslim candidates for this year's presidential race.

While there are some accusations that the Christian-to-Muslim transition stems from corrupt deal-making, there is also a sense that even a crude check on long-term dominance by any regional or ethnic group may be better than a free-for-all.

"If I have my chance, I'll try to do good by you. If you do my people bad, I'll do bad for you," said Innocent Ike, 25, a Christian who works in a bookstall selling Bibles. "Now we all do good works for each other."

The 140 million people of Africa's most populous nation are roughly split between the Christian-dominated south, once controlled by Europeans, and the Muslim north, where Arabs traveling across the Sahara Desert established their footholds. Followers of traditional, animist religions make up a small minority.

Religious and ethnic intermarriage is common, and many communities boast mosques and cathedrals. But religious violence has flared frequently since divisions largely tamped down by military regimes flourished in a budding democracy. In February, clashes between Christians and Muslims left at least 127 people dead in several cities, the violence provoked by the worldwide uproar over cartoons of Muhammad in a Danish newspaper.

Religious identity is so sensitive that Nigeria's secular government did not include it on a census taken last year. Detailed results released this month showed northern states with 75 million people to the south's 65 million - findings promptly rejected by state governments across the south.

After decades of military rule, the April 27 election is meant to be the first time an elected leader hands power to another in Nigeria. Incumbent Olusegun Obasanjo is prevented from running again by term limits.

Most of the military regimes were led by Muslim northerners, since Britain largely staffed the pre-1960 independence army from the north. Ahead of the 1999 elections, political leaders reportedly brokered an agreement that made Obasanjo the consensus candidate.

"After the end of rule by northern Muslims . . . quite a number of people even in the north believed that the northerners had made a hash of things and it was time to have a southerner in charge," said Junaid Muhammad, a former lawmaker.

Obasanjo's People's Democratic Party nominated for president a largely unknown official from the north, Umaru Yar'Adua, the governor of Katsina state. Yar'Adua, seen as the front-runner because of his party's dominance, has chosen a southern Christian, Goodluck Jonathan, as his running mate. The current vice president is Muslim.

"We have respect for the Muslim religion and Christians and for nonbelievers, and we try to accommodate all to ensure the country remains one," said John Odey, a spokesman for Obasanjo's party.