Raila Odinga-led ODM party will kick off its nominations on Friday, April 1, that will run for 20 days.
The party, a member of the Azimio la Umoja coalition that brings together over 26 outfits, will only hold primaries in 20 counties perceived to be its strongholds.
A schedule released by the party's National Elections Board (NEB) shows that the polls, which could make or break it depending on how it manages them, will take place on Friday in Nakuru.
They will be followed on Monday next week in the coastal counties of Kilifi, Taita Taveta and Kwale, and in Mombasa on Wednesday.
The process will run up to April 21, a day before the deadline imposed by the Independent Electoral and Boundaries Commission (IEBC) for holding primaries.
ODM nominations will also take place in Kisii, Nyamira, Turkana, Migori, Bungoma, Trans Nzoia, Vihiga, Busia, Kisumu, Kakamega, Siaya, Homa Bay, Narok, Kajiado and Nairobi.
In the 27 counties where primaries will not take place – mainly in Mt Kenya, parts of Rift Valley, Ukambani and North Eastern – ODM has used consensus in some cases to select candidates while it will not field candidates in others but will rally behind its partners.
NEB chairperson Catherine Muma said the party was encouraging its aspirants to try consensus in order to reduce disputes.
That is the only way "that as a party we (can) move forward knowing that an electoral position can only go to one person. We encourage members to speak to each other so as not to be negatively competitive to each other," she said.
She also said that although the party had commissioned opinion polls, it was yet to deliberate on the results and decide who will be given direct tickets based on the surveys, adding that if they get strong aspirants joining them from other parties, they will give them direct tickets.
With the new political parties law requiring outfits to allow only their registered members in primaries, Ms Muma said they will apply it under universal suffrage.
"For our party, we are going to use the register of ODM members,” she said, adding that the nomination schedule is not cast in stone “because the process of consensus continues".
The new law is a setback for aspirants.
It was supported by the Azimio la Umoja camp and fiercely opposed by Deputy President William Ruto’s team.
Political parties are required to apply in writing to the Registrar of Political Parties for a certified copy of the register of members at least 21 days before the date of nominations.
While parties had 7.6 million registered members in 2013, the number has shot up to 24.8 million, said Registrar of Political Parties Ann Nderitu.
Some 15.4 million are men and 9.4 million women, figures that will be key in party primaries.
In areas where ODM will have achieved consensus, Ms Muma said the party will return nomination fees to aspirants who step down.
DP Ruto's United Democratic Alliance (UDA) will hold its primaries on April 14 and Musalia Mudavadi's Amani National Congress (ANC) on April 12-20.