The nomination of Siaya Count Governor Cornel Rasanga has been nullified by a tribunal that ruled that the primaries were not free and fair.
The Political Parties Disputes Tribunal on Friday evening directed that the exercise be repeated within 72 hours.
The nomination of Mr Rasanga was petitioned by a voter, Mr Jeconia Ogutu.
Mr Rasanga was on Thursday cleared to contest in the August elections by the Independent Electoral and Boundaries (IEBC).
In the primaries, the governor competed against Rarieda MP Nicolas Gumbo and other candidates.
Mr Gumbo lost the primaries and sought to seek election for the governor seat as an independent candidate. He has since been cleared by the electoral agency.
The tribunal directed ODM to use its party machinery to nominate a candidate.