In a bold but legally risky gamble, Nasa bets its immediate electoral future on 2013 Supreme Court judgement, which treats withdrawal and death of a candidate as the same - both requiring a restart of the election.
How did we get here?
Kenyan opposition leader Raila Odinga's withdrawal from a repeat presidential election is the latest in a series of dramatic developments over the disputed vote:
Tense vote
Kenyan voters turn out in large numbers on August 8 after a tight race between President Uhuru Kenyatta and Odinga, his long time rival.
There are fears the bad-tempered campaigning will lead to violence. More than 1,100 people were killed in politically motivated tribal violence after the 2007 election.
Early results give Kenyatta a comfortable lead but are immediately rejected by Odinga, who claims hackers broke into the electoral commission database and manipulated the results.
The official results are published on August 11 and give Kenyatta 54.27 per cent of votes to Odinga's 44.74 per cent.
Angry protests erupt immediately in Odinga strongholds. The violence continues for days. The Kenya National Commission on Human Rights says 37 people are killed, most of them by the police.
Historic annulment
Odinga takes his complaints to the Supreme Court. In a shock announcement, its judges on September 1 declare the results of the poll "invalid, null and void" and orders a re-run within 60 days.
The annulment is a first for Africa.
The date for the new election is later announced as October 17.Â
A confidential memo in which the Independent Electoral and Boundaries Commission (IEBC) admits to irregularities and failings in the conduct of the vote is made public on September 7.
Uncertainty
As doubts grow over Kenya's ability to hold a rerun of its presidential election, the French biometrics firm OT-Morpho that provides the electronic voting system says on September 18 it will not be ready in time.
The opposition slams the move as an effort to render legal some of the "irregularities and illegalities" cited in the Supreme Court's cancelling of the vote.
Protests erupt in early October as Odinga calls on his supporters to pressure the government to overhaul the election commission, threatening he will not take part in a re-run otherwise.
On October 10 he withdraws from the re-run, saying the election panel has failed to make needed reforms.
But he also indicates this does not mean his battle is over, citing legal arguments his party believes will compel election officials to begin the whole process from scratch.