National Super Alliance (Nasa) co-principal Moses Watangu’la now says he will defend his Bungoma Senate seat.
Mr Wetang’ula on Friday said he would run for the county seat on his Ford-Kenya party ticket.
The veteran politician had left political pundits and Bungoma residents guessing the fate of his seat, with speculation rife that he had appointed one of his allies to take it.
Mr Wetang'ula’s declaration means he has a fallback position in case Nasa fails to wrest power from Jubilee.
He had been named deputy premier CS responsible for coordinating economic affairs in the line-up of Nasa if it wins in August.
Mr Wetang’ula said by defending his seat, he was being strategic in preparation for the 2022 presidency.
"When you see a ram moving away, don't think that it’s a coward, its preparing itself to hit its rival very hard," he said at Kanduyi market in Bungoma.
“By defending my seat, I’m not a coward, even my friend, the Bomet governor, will be defending his.”
He continued, "We have already endorsed Raila Odinga as the Nasa presidential flag-bearer and we will change the constitution to allow another co-principal to take over in 2022."
The Senate minority leader will face off with three other candidates who are eying his post.
They include businessman Juma Mukhwana of the Jubilee Party and veteran journalists David Makali and Boniface Nyongesa.
Mr Nyongesa recently resigned as the head of Sulwe FM, a Bukusu vernacular radio station owned by Royal Media Services.
Mr Makali will be vying for the seat for the second time on the Amani National Congress ticket after he was defeated in the 2013 by-election Mr Wetang’ula.
This was after former Webuye MP Musikari Kombo successfully challenged in court Mr Wetang'ula's victory in the March 4, 2013 elections.
“Mr Wetang’ula should prepare himself for a resounding defeat,” said Mr Mukhwana.
“He should not be cheating us that he is going for the presidency but returns to vie for a smaller seat, he should be disappointed, I will give him a run for his money.”
Resident Benard Wakamala said Mr Wetang’ula is a big let-down to the Luhya community and should not be taken seriously at all.
“He launched his presidential ambition at Muliro Gardens in Kakamega, now he is telling us that he wants to defend his senatorial seat. He is a joke,” he said.
“Let us vote for other serious people who can drive the development agenda of this country.”
Fred Wekesa, a Ford-Kenya supporter, said the politician had made the right decision to defend his seat.
“I see nothing wrong,” he said.