Mrs Ngilu apologised to residents “for betraying the Kamba in 2013 by opposing Mr Musyoka”.
Ukambani leaders on Tuesday piled pressure on the National Super Alliance to name Wiper chief Kalonzo Musyoka the presidential flagbearer.
Former Lands minister Charity Ngilu, Machakos Senator David Musila, Kitui Governor Julius Malombe, Chama Cha Uzalendo leader Wavinya Ndeti, Machakos Deputy Governor Bernard Kiala and People’s Trust Party leader Mutua Katuku spoke at a rally in Emali in Makueni
“I cost the opposition the 2013 election by delivering 100,000 votes to the other side. I will never do that again,” she said.
Others at the meeting were Mr Musyoka, governors Kivutha Kibwana (Makueni) and his deputy Adelina Mwau, Nairobi deputy governor Jonathan Mueke, Makueni Senator Mutula Kilonzo Jr and several Members of Parliament.
Prof Kibwana said the Wiper leader would tackle corruption and develop Kenya.
He said the Kamba should make use of their 2.5 million votes to propel Mr Musyoka to State House.
“We don’t want to see these votes go to waste,” Prof Kibwana said.
Ms Ndeti revisited the 2013 agreement in which Orange Democratic Movement leader Raila Odinga was to be the Coalition for Reforms and Democracy flagbearer and then pass the baton to Mr Musyoka this year.
“It is time the deal is honoured and Kalonzo flies the opposition flag,” she said.
Mr Musyoka said the solidarity exhibited by lower eastern leaders on Tuesday had given him confidence to go for the top seat.
He described Kamba leaders not supporting him as traitors and untrustworthy.
Senator Kilonzo Jr said: “To Ukambani leaders who are not with us, you are finished.”
East Africa Legislative Assembly member Peter Mathuki said he was ready to step down for either Ms Ndeti or Mr Kiala in the race for Machakos governor if Wiper primaries showed that he was not the strongest aspirant “in order to promote party unity and guarantee Mr Musyoka victory in the presidential race”.
“Kalonzo has sacrificed enough for others. It is time they also sacrificed for him,” he said.