Borana Council of Elders wants all clans from the community not to back the incumbent senator in Friday's Jubilee Party nominations.
The elders instead want the clans to support former Tana and Athi-Rivers Development Authority (Tarda) chairman Abdul Bahari.
The elders are not happy with Senator Mohammed Kuti's sudden decision to vie for governorship.
Dr Kuti, who has fallen out with the incumbent Governor Godana Doyo since their 2013 alliance on the defunct United Republican Party (URP) ticket, is a late entrant in the race.
Still, the senator has caused ripples especially in cosmopolitan Isiolo town and his campaign machine is well oiled and heavily funded.
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This has not gone down well with his rivals and the elders, who are now challenging the senator to explain why he is running for the seat against his former ally, Doyo.
Drawn from the communities 17 clans, the elders met at Kambi Garba Resort last weekend where they came up with the declaration aimed at taming what they view as Kuti's growing influence.
After meeting for two days, the elders summoned all aspirants eyeing various seats from all political parties to the gathering on Monday where they announced their decision.
Among those who attended the meeting were Bahari, Doyo who has since decamped to Party for Development and Reforms (PDR), Hussein Golicha (Kanu) and Adan Kabelo (ODM).
The elders also approved Doyo's move to PDR describing it as 'a friendly' party. The aspirants who were present were not allowed to speak to the Press by the elders.
The Council of Elders' chairman Abdullahi Gonjobe clarified that the declaration only affects Jubilee's governor ticket during the nominations.
The elders decision follows major inroads made by Kuti who comes from the Sakuye clan, and who is heavily relying on non-Borana votes to clinch the nomination ticket.
Gonjobe said the council would meet again next month to decide who to back among its candidates (Doyo, Bahari, Golicha and Kabelo) in the August polls.
The region's politics is heavily based on clanism.
Although Kuti's Sakuye speaks Borana language and share similar culture, it is listed as different tribe under the National Population and Housing Census.
Although nearly 65 per cent of the 74, 458 registered voters are Borana clans, the Turkana, Meru, Somali and Samburu provide the swing votes.
The Sakuye also hold a considerable number of votes.
But Kuti dismissed the declaration as tribal accusing his rivals of ganging up against him after sensing defeat.
''My line-up represents the face of Isiolo and that is why I have the support of the majority of all the communities. All the people of Isiolo must be represented equally," he said.