Senator Hassan Omar claims he has the blessings of Raila Odinga and Kalonzo Musyoka to contest the governor's seat.
On Sunday, Mr Omar accused Governor Hassan Ali Joho of using attacks on President Uhuru Kenyatta to mask his development record.
Omar accused Joho of branding him a Jubilee mole.
"Joho has attacked President Uhuru and Ruto and branded me a Jubilee mole to conceal his administration's failure to deliver," Omar said.
Addressing a rally at Bomani ground in Likoni constituency, Omar said he had no problem with Joho's Orange Democratic Movement (ODM) but was opposed to the governor's leadership style.
Earlier, Omar had said Raila and Kalonzo were counting on him to win votes for the National Super Alliance (NASA) in the region.
"Raila and Kalonzo have expressed confidence in me and given me their blessings to seek votes in Mombasa that will see Raila have a landslide win in the county," he said.
Raila campaigns
The senator claimed Governor Joho, a bitter critic of the Jubilee administration, was riding on Raila's campaign rallies including the one planned for Mombasa on Thursday.
The senator endorsed Raila and Kalonzo as the next president and deputy in the rally, saying his rival, Joho, was not doing enough to market NASA's candidate.
"Joho is used to hosting small-time rallies where he tells people nothing but hides behind the NASA mega campaigns," said Omar.
The senator said he was best placed to bring change to the county and had numerous winning strategies.
Omar said a recent petition seeking to bar him from vying for the governor's seat was political.
"The timing of this petition smells politics. There is nothing it aims to achieve; I have won the first instance and I will still win the race for governor," said Omar.
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[Joackim Bwana and Patrick Beja]