Nominated Senator Naisula Lesuuda has decamped from Jubilee Party to Kanu, under which she will seek election as Samburu West MP.
Lesuuda announced on her Facebook page that the light she had kept burning "beneath a table" was "finally out".
The politician, who was nominated in 2013, said she will launch her bid in Maralal in a few days.
"For the many out there who believed, kept the faith even when the road looked impassable, thank you for pressing on," she wrote.
"Your resolve and belief has seen an unstoppable movement that will see the people get the leadership they honestly deserve."
The former TV personality had been an ardent supporter of the Jubilee government and wanted President Uhuru Kenyatta re-elected.
Lesuuda had said last September that she would vie on a Jubilee ticket against current MP Lati Lelelit.
She also said that being married has never been a leadership quality and asked residents to look at her as a leader, not a young girl who is not married.
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Senators, who hoped they were an exalted Upper House, are abandoning the Senate in droves and making a mad dash for more lucrative and powerful positions. Even MCAs.
The Senate has been nicknamed Nyumba la Wazee, House of Retirees. Senators control no resources.
They leave behind power struggles with the National Assembly that seeks to curtail the enfeebled Senate and sap its already limited powers. At times there's talk of scrapping the Senate altogether as a superfluous contributor to the ballooning wage bill.