Former Orange Democratic Movement (ODM) point man in Meru Mike Makarina has accused the opposition of plotting to plunge the country into chaos.
He defected to Jubilee last week.
Speaking two days after he was received by President Uhuru Kenyatta, Mr Makarina said the opposition's push for changes in the electoral commission were aimed at disrupting the repeat election.
"I am fed up with supporting the opposition because of their obsession with demonstrations. We welcomed the Supreme Court ruling but Nasa leader Raila Odinga has refused to prepare for the election. I consulted widely with other Nasa supporters in Meru and we decided to cross over to Jubilee. Nasa's demands may lead the country into chaos," he said on Monday.
But ODM officials in Meru downplayed the defection, saying the opposition was intact and more organised than in the previous election.
Mr Makarina, who has been vocal on the rights of persons living with disabilities, said he ditched the opposition after President Kenyatta promised to address challenges affecting the disabled.
"What took me to the opposition was the failure by the government to help the disabled access education and government opportunities. President Kenyatta has asked us to meet him in State House so that we can express our concerns. He has also promised to deal with runaway insecurity in Tigania East," he said.
Mr Makarina said the defection to Jubilee would substantially reduce Nasa presidential candidate Raila Odinga's votes on October 26.
In the August 8 election, Mr Odinga garnered 55,000 votes in Meru County up from the 32,000 votes he got in 2013.
Nasa coordinator in Meru Joseph Mung'athia said those who have defected have always been pro-Jubilee.
"I can confirm that the Nasa leadership in Meru is intact. Some people who claim they are leaders are not. None of the Nasa officials have defected and Mr Makarina was a member and activist but not part of the county leadership," the officials said in a statement.
Mr Mung'athia said Nasa supporters in Meru were prepared to ensure more people vote for Mr Odinga.