By Joseph Winter
BBC News, Sudan
A single woman in a bar would be doubly shocking in north Sudan
A referendum due in 2011 on whether South Sudan should leave the rest of the country is seen as a major tuning-point in the country's history - but some suggest that nationwide elections due two years earlier could prove even more important.
The leadership of the former rebel Sudan People's Liberation Movement, which now runs the south, is meeting to decide its future policies.
Mainly animist and Christian South Sudan feels like a completely different country to the largely Muslim, Arab-speaking north.
Visitors need a separate visa for the two regions and the writ of the authorities in Khartoum counts for hardly anything south of the internal border.
In the southern capital, Juba, the most common mobile phone network is operated from Uganda, with a +256 code, not the +249 for Khartoum. Calls to Uganda are charged at a local rate, while those to Khartoum are international.
The northern Sudanese networks do not work very well in the south, which were cut off for during the 21-year war, which ended in 2005.
During the conflict, aid agencies ran their operations from Kenya and many southerners have more links to neighbouring countries than northern Sudan, so the Ugandan mobile set-up suits them very well.
While the north is subject to Islamic Sharia law, with the streets of the capital deserted after 2000 at night, alcohol and nightclubs are easily found in Juba, a sleepy provincial town which is experiencing a massive building boom in case it becomes an international capital in four years' time.
Gaudy neon signs can be seen flashing in the giant mango trees which line the River Nile, while huge stacks of speakers blare out the latest rap and R 'n' B releases from Kenya and the United States.
Under a 2005 peace deal, the SPLM is running South Sudan until the referendum and joins President Omar al-Bashir's National Congress Party in a government of national unity.
It has been generally assumed that the plebiscite was bound to lead to independence but SPLM officials are not taking that for granted.
"If we win elections, and a southerner becomes national president, we would no longer have any reason to leave," one senior SPLM official who did not want to be named told the BBC News website.
The same prospect is raised by several former SPLM fighters.
With just two years to go before the elections are due, there is little sign of much preparation.
But SPLM spokesman Samson Kwaje is confident that the elections will take place and says his movement is taking advantage of the peace to build up nationwide structures.
"We are busy trying to transform ourselves into a fully fledged political party. We are recruiting members nationwide," he said.
Preparations for the polls are behind schedule but work has begun on a national census, which would enable officials to divide the country into constituencies.
Sudan analyst Alex de Waal says the international community is making a serious error concentrating so much on the conflict in Darfur and ignoring the polls which could transform the country.
"This is the most crucial issue in Sudan," he told the BBC News website.
Salva Kiir does not have the charisma of John Garang
Although the SPLM was vilified in government-controlled areas during the war, Mr de Waal says they would win a reasonable number of votes in the north, to bolster their southern heartlands, and so could win a nationwide majority.
But could a southerner really win national elections against the NCP, which has been in power since a 1989 coup?
"In a popular vote, the SPLM would defeat the NCP, but they are badly organised," says Mr de Waal of the New-York based Social Science Research Council.
"The NCP is deeply unpopular."
Nevertheless, Mr de Waal says that no single party can hope to win an election on its own.
He says the SPLM must forge an alliance with one of three groups:
Mr Kwaje says the SPLM has not yet decided which groups, if any, it will contest the elections with.
- The NCP;
- The northern opposition, which it already has links to;
- The non-Arab groups in Darfur and the east - assuming it is possible to hold elections in Darfur.
He said it would depend on the other groups' manifestos and, of course, how capable they are of delivering votes.
On a possible alliance with the NCP, he says it depends on how the peace deal is implemented.
Earlier this year, southern leader Salva Kiir made an angry speech, accusing the NCP of not keeping its side of the bargain.
Some analysts say that renewed conflict is more likely than national elections.
But Mr Kwaje dismissed such fears and said relations between the SPLM and the NCP were improving.
Senior NCP official Ghazi Salahuddin told the BBC his party was "disposed to have an alliance with the SPLM".
This would probably be a winning combination of the SPLM's popularity and the NCP's organisation but who would be their presidential candidate?
Charismatic former SPLM leader John Garang would have been a strong contender but he died just a few months after the peace deal was signed, to be replaced by the rather dour Salva Kiir.
If the SPLM is to achieve its dream of winning the presidency, it should find an alternative candidate, says Mr de Waal.
Khartoum street vendor Osman agrees that Garang would have made a stronger candidate but says he would still prefer Mr Kiir to Mr Bashir.
He says the racial and religious differences would not be a factor in his vote.
"We are all Sudanese - I trust Kiir," he said as he struggled to sell a box load of digital watches.
Juba is changing from a sleepy town to a capital city
Mr Salahuddin says he sees no reason why a southerner could not become national leader in future elections but "as of now, our only candidate is Bashir."
He does admit, though that a southern leader could make unity "more attractive".
Mr Kwaje says the peace deal explicitly forbids any party campaigning to remove Sharia law in northern Sudan but does not rule out adding that to the SPLM manifesto in future - if the south remains part of Sudan.
He insists, though, that even if a southerner does become national president, the referendum would still be held.
"We will still give the people the chance to decide."