Labour, the bookies' favourites to regain the seat they lost by just 590 votes in 2011, will select their candidate from an all-woman shortlist this afternoon. The Nationalists choose theirs tomorrow.
The Labour contenders are Fife councillors Cara Hilton and Lesley Laird, and Crown Office solicitor Fiona Yates. All are from political families.
Hilton, 38, who works for Dunfermline's Labour MP Thomas Docherty, is the daughter of former Falkirk MSP Cathie Peattie. Yates, 43, is the daughter of Cowdenbeath MSP Helen Eadie. Her husband Gavin is also a Labour councillor, and her grandfather was a Labour MP.
Laird, 54, is the daughter of former STUC chairman John Langan.
Shirley-Anne Somerville, who was a list MSP for the Lothians from 2007-11 and is currently director of communities at the Yes Scotland campaign, is the frontrunner for the SNP selection. The SNP said their shortlist would be finalised tonight.
As part of their commitment to gender balance in Parliament, Labour originally shortlisted the three female contenders last week, but then reopened the process to both sexes, attracting applications from former Edinburgh City Council leader Ewan Aitken and former Lothian police inspector Tom McInally. However, the party yesterday reverted to the original all-woman shortlist and the men were excluded.
On the social media site Twitter, McInally agreed with another user that the process was "pretty chaotic".
The candidate the SNP feared most - Fife's Labour Provost and former Dunfermline FC manager Jim Leishman - declined to stand.
The SNP face an uphill fight, with Labour needing just a 1% swing to regain the seat.
Walker won Dunfermline for the SNP on the crest of the party's 2011 landslide thanks to LibDem switchers.
The SNP's vote share jumped 13.5%, while the LibDem vote slumped by 13.5%.
A tactical vote by LibDems for Labour - perhaps as part of an unspoken pro-Union alliance - would mean defeat for the SNP.
Meanwhile, ministers were yesterday urged to review the prosecution of domestic violence in light of the Bill Walker scandal.
Scottish LibDem leader Willie Rennie said the former Dunfermline MSP's prosecution in a lower court, where he faced a maximum 12 months in jail despite his conviction on 23 counts of assault, had exposed a problem with the current system.
In future, Rennie said the Crown Office should be allowed to consider the cumulative impact of years of abuse when deciding how to prosecute offenders.
"Too often, violent incidents are treated as isolated events. The Bill Walker case has made clear that frequently this is simply not true."