Nominated Senator Elizabeth Ongoro has defected from ODM citing frustration by the party.
Sources within Raila Odinga's party said Ongoro was asked not to run for the Ruaraka MP seat but refused. The seat is held by TJ Kajwang'.
The sources said Ongoro turned down offers to vie for woman representative or senator.
The legislator accused ODM of denying her the chance to exercise her democratic right to seek the Ruaraka MP seat.
She was apparently barred from contesting on disciplinary grounds.
This was after her supporters clashed with those of Kajwang' in Mathare last month, leaving two people dead.
Ongoro is expected to announce the party under which she will vie for MP. The sources said she will join a party in the National Super Alliance.
Her defection will
deal ODM a big blow as her mobilisation skills had turned her into an asset for the party.
Ongoro declared interest in the Ruaraka seat following speculation that Narc Kenya leader Martha Karua was to go for Nairobi Senator.
Karua said she was not allied to the Opposition or Jubilee Party but is supporting President Uhuru Kenyatta's re-election.
The Narc-K leader, who is former Gichugu MP, will vie for Kirinyaga governor, a seat that former Devolution CS Anne Waiguru is also eying.
Several politicians including Kitutu Chache South MP Richard Onyonka and Gitobu Imnayara have defected from Raila Odinga's ODM party ahead of the August 8 general election.
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But others, including Nairobi businesswoman Esther Passaris,
have "returned home" to the Orange Party.
Passaris who wanted to vie for the Nairobi governor seat, said she will run for Nairobi woman representative.
"For Kenya to be united we must choose baba (Raila Odinga) as the NASA presidential candidate," Passaris said at Kibra on Sunday.
"I have returned home to ODM.
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