Kamukunji MP Yusuf Hassan has quit the Jubilee Party for former Deputy President Rigathi Gachagua's Democracy for Citizens Party (DCP).
The move could reshape political alignments in Nairobi ahead of the 2027 General Election.
Gachagua formally received Hassan into DCP on Tuesday, August 25, at the party's headquarters in Nairobi, presenting him with a DCP cap before supporters and officials.
"I am happy to join DCP, a party which is advocating for the good of Kenyans. It is looking for the change we want since Kenyans have suffered due to high cost of living," said Hassan.
He cited unemployment and heavy taxation among his concerns.
"Kenyans have told me they are tired of this burden including corruption and bad politics. We want better lives. We will soldier on today as we strive to win the next elections," he added.
Hassan denied his opposition to President William Ruto stems from personal grievances tied to Gachagua's impeachment.
"I have nothing personal against William Ruto. I have everything against what he stands for and what he does. I want good leadership in this country. And I'm offering myself for that position of president," he explained.
He warned politicians stoking tribal divisions that Kenyans have lived and worked together for decades.
"We live together as Somali people and trade with all tribes including Kikuyus. We live in their houses and even marry one another," he noted.
Hassan won a fourth consecutive term as Kamukunji MP in 2022 on a Jubilee ticket, garnering 34,264 votes, or 56.23 per cent of the vote.
UDA's Hassan Robow Mohamed came second with 22,644 votes.
He first won the seat in 2011 on a Party of National Unity ticket, before moving to The National Alliance in 2013 and then Jubilee in 2017.
The defection comes as Gachagua steps up efforts to turn DCP into a national political vehicle and strengthen his hand in talks over a united opposition front against Ruto.
It also comes amid disagreement among opposition figures over who should lead a coalition to challenge Ruto in 2027.
Gachagua has rejected suggestions that his role should be limited to helping another opposition leader defeat Ruto before handing over power.
"Rigathi is not a kingmaker. Gachagua is king," he declared on Monday.
Gachagua said he had seen supporters of his opposition allies advancing what he called a "ridiculous proposition" that his job was merely to remove Ruto and hand the presidency to someone else.
"Many people, including supporters of my colleagues in the United opposition, I have seen them on social media and in public platforms advancing a ridiculous proposition: that his work is to remove William Ruto and give leadership to others," he observed.