Umaru Yar'Adua (C) had success in combating oil militantcy
Nigerian President Umaru Yar'Adua has returned to the country after three months in hospital in Saudi Arabia.
Rival factions have been vying for influence in the power vacuum he left behind - provoking a political crisis.
Will his return solve the crisis?
In a clear-cut scenario, a fit and healthy Umaru Yar'Adua will resume his presidential duties, his critics will be satisfied and the crisis will pass.
YAR'ADUA ILLNESS TIMELINE
23 November 2009 Goes to hospital in Saudi Arabia
26 November Presidential doctors say he has pericarditis - inflammation of the heart lining
23 December First court case filed urging him to step down
5 January 2010 Two more court cases filed, rights group wants president declared "missing"
12 January President gives first interview from Saudi Arabia
27 January Cabinet declares president fit
29 January Court says no need for formal transfer of power
9 Feb: Vice-President Goodluck Jonathan becomes acting president
24 Feb: Yar'Adua returns
His powerful backers will be doing all they can to get him back on his feet to ensure that this happens.
They will be looking for the president to make it through to an election planned for next year to avoid any more wrangling.
However, Mr Yar'Adua has not been seen in public since November.
His return to the country was shrouded in secrecy, being rushed away from the airport in an ambulance in the middle of the night. Even ministers have been kept in the dark.
Although officials say his health has "greatly improved", many Nigerians are deeply sceptical that he will ever be able to resume his duties - some have even suggested that he has already died.
The manner of his return to the country is unlikely to placate them.
The crisis is likely to continue for some time yet.
What has happened in his absence?
All sorts of rival groups have had a tilt at grabbing a little bit of power, influence, or fame.
Goodluck Jonathan has taken over leadership on a temporary basis
Members of the National Assembly became embroiled in a row over whether or not Mr Yar'Adua needed to formally hand power to his deputy.
Rights groups launched legal bids to clarify the constitution - one group suggesting the president should be declared "missing" and a search party be sent out.
For weeks, the country stagnated and no-one was really sure who was in charge.
Ultimately, politicians decided that an interview the president conducted with the BBC from his sick bed was notice enough, and declared Vice-President Goodluck Jonathan to be acting president.
So far, Mr Jonathan appears to have been grudgingly accepted as the best compromise, and a measure of stability has returned.
Indeed, in a rare bid to provide clarity, the presidency has spelled out that he remains in charge, while Mr Yar'Adua "recuperates".
Why has it all been so murky?
Democracy has struggled to take root in Nigeria, where the military only relinquished its grip on power a little more than a decade ago.
The young democracy has been characterised by ill-defined constitutional rules, rampant corruption, weak institutions and an opaque political culture where leadership changes hands through backroom deals.
In such circumstances, being in power - at whatever level - is seen as the best way of becoming wealthy in this oil-rich country, so the stakes are huge for a lot of people.
This proved to be fertile ground for a political crisis in the president's absence.
How has the crisis affected ordinary Nigerians?
The people are used to political instability. They are also used to being kept out of the loop by power-brokers at the top of the political tree.
But the latest crisis is unprecedented, even by Nigeria's standards.
There have been large scale protests in major cities, thousands of people demanding that power be handed to Mr Jonathan.
And crucially, the lack of leadership has threatened talks with militants in the Niger Delta, where the oil is produced which makes Nigeria one of the world's major exporters.
Mr Yar'Adua had made it his personal project to bring peace to the delta, and the process has stalled in his absence.
One of the militant groups launched an attack on an oil pipeline in December, saying it was a "warning strike" over what it called government delays in progressing with peace talks.
And a militant group ended its ceasefire at the end of January.