How many voters will be eligible to vote in the Nigerian elections that start on Saturday? That is the key question people here have been asking for months. It is particularly important because the last official census was conducted in 1963, and nobody knows precisely how many Nigerians there now are.
The answer is potential political dynamite, as the geographical concentration of votes could swing a close and hard-fought election in favor of one of the tribal and regionally based parties.
Registering a largely rural and illiterate electorate spread over an area the size of both California and Texas was a huge job.
In the north there was a problem registering Muslim wives normally kept in purdah.
The Federal Electoral Commission (Fedeco) completed the national registration barely 10 days before the elections.
When it announced there would be 65 million voters, there was a general gasp of surprise. There are 38 percent more voters than at the last elections four years ago.
It also signifies that Nigerian's population is at least 130 million, compared with earlier estimates of 80 to 100 million.
One man who is not surprised is the presidential campaign director of the ruling National Party of Nigeria (NPN), Umaru Dikko. ''It shows greater political awareness among Nigerians,'' he said. Many people regarded the 1979 elections as merely another military exercise. After 13 years of military rule they were unaccustomed to democratic elections.
Many others living in isolated rural areas knew nothing of the elections or lacked transportion to the polling booths.
As a result only 20 percent of the registered 47 million voters actually voted.
The turnout in 1983 is expected to be higher. But observers suspect that the registration figure is grossly inflated. ''There must be many millions of phantom voters with Kano, Kaduna, and Lagos the biggest ghost towns,'' they said.
But with all parties using the same tactics it is hard to see which party stands to benefit.
For its part, Fedeco intends to prevent multiple voting by marking each voter's thumb with indelible ink.
No voter will have to walk more than 5 kilometers to the nearest polling booth. There are more than 150,000 polling booths spread across the country - one for every 500 voters.
Many of the booths are rough wooden shacks without electricity or other amenities. But the votes will be counted in the booths and darkness falls early, so light will be essential.
The federal government has accordingly ordered 400,000 hurricane lamps - apparently considering them more reliable than the National Electric Power Authority, whose cutoffs are proverbial.
Voting slips will carry the symbol of each party, in addition to the names of candidates, to guide the many illiterate voters. The ruling NPN is represented by a house surrounded with corn. The symbol of the opposition Unity Party of Nigeria is a torch, and the Nigerian People's Party shows a family group. Billboards carry large pictures of candidates and party symbols and the shortest of slogans. ''Vote for a winner - President Shehu Shagari'' appeals to the African voters' natural instinct to be on the winning side.
Unlike US elections, television has comparatively little influence. It is beyond the reach of most people, and it is heavily biased in favor of the federal government.
With a few exceptions the country's prolific press is also heavily partisan and is read mainly by party supporters.
The radio tends to be less virulent and reaches the widest audience.
The news media have helped whip up fears of escalating violence, especially when the results are announced.
To make it more difficult to rig results by stuffing or switching ballot boxes, the opposition parties have insisted that votes be counted on the spot rather than in a regional center.