He is one of the leading think tanks in Raila's quest to checkmate President William Ruto's regime and a towering political colossus whose rise to political stardom has left many baffled.
While his supporters and allies are cheering him on, critics believe he has a long way to go to stamp his authority, if he is keen to step into Raila's big political shoes in the future.
Last week, Wandayi's rise was confirmed by Raila's elder brother Oburu Oginga, who appears to endorse him as a potential successor of the ODM leader in Nyanza.
According to Oburu, Wandayi, who is also the Minority Leader in the National Assembly is the only politician who understands what his party leader wants. Oburu says that, unlike other politicians who always ask Mr Odinga to give them direction on political matters, Wandayi is always ahead of them.
"My friend Opiyo has never waited to be told what his party leader wants but he knows how to read his body language," said Oburu.
The Senator, who is also the opposition chief's elder brother, said the Ugunja lawmaker has a bright political future.
He added that Wandayi, who is serving his third term, was not only sharp but is charting his own political path.
"He learned politics in the footsteps of Mr Odinga immediately after he left the university and we are convinced that he is the right person to take over the region's leadership," said Oburu.
While applauding Wandayi for being loyal to the Orange party, Oburu hit out at those calling on Mr Odinga to appoint the community's political kingpin.
"You cannot be appointed to be a kingpin but you can work your way out just like Mr Odinga did. I am happy that Mr Wandayi who is younger than some of the political leaders from the region is on the right track," said Oburu.
In last year's general elections, Wandayi was touted as former Governor Cornel Rasanga's successor before he shelved his ambition for James Orengo.
On Tuesday, Wandayi told the Standard that the position he holds at the National Assembly has placed key responsibilities on his shoulders. He claims he has learned his trade from Raila and is willing to go full stretch to serve the interest of Kenyans.
"It must be understood that I am a political student of Raila Odinga. I am passionate about social justice and democratic governance. I am driven by the desire for an equitable society. Therefore, I can never shy away from saying things as they are," said Wandayi.
He claimed that he has been keen to use his position as the leader of the Minority in the National Assembly to shape public discourse on pertinent issues.
"The position has placed on my shoulders enormous responsibility to not only advance the cause of our political movement but also to champion the interests of the general public. I feel I have done my best, so far," he said.
Stay informed. Subscribe to our newsletter
In Nyanza, the Ugunja MP has been on an overdrive as he consolidates support for the ODM party in a region the party considers its traditional stronghold.
In the last three weeks, Wandayi has held meetings with ODM delegates in Kisumu, Siaya, and Migori, while also rallying other ODM members to strengthen the party and ward off UDA's forays.
According to Wandayi, they will do everything to ensure they safeguard the support ODM enjoys in Nyanza.
"My party remains ODM, where I serve as the Secretary for Political Affairs. It's my duty to contribute to its growth in every part of the country. This is a role that I continue to play with a lot of enthusiasm. Nyanza is one of our strongholds and we have a duty to protect it from political scavengers," said Wandayi.
The Standard has established Raila's ODM party has lined up a series of activities, targeting to rejuvenate its grassroots support. This includes planned meetings across the region, aimed at strengthening the party amid a sustained onslaught by the UDA party.
Last week, ODM leaders continued with their efforts to strengthen the party in the region and conducted meetings in Ugunja and Nyatike constituencies.
The move is part of a pushback against President William Ruto's UDA party that has sustained an onslaught in Raila's backyard. While Ruto's troops are optimistic that they are making fruitful incursions into Nyanza and Gusii, Raila's allies in ODM believe the efforts are a waste of time for the ruling alliance.
They claimed the region is firmly behind the ODM chief and remains one of the key bases for Azimio.
Led by Minority leader Opiyo Wandayi, the party moved to Nyatike Sub-County where UDA has been calling on electorates to jump ship and join the Kenya Kwanza government by registering as UDA members.
Critics of Wandayi, however, dismiss his rise and claim he does not sway a lot of support. In a recent interview with ODM chairman John Mbadi, the legislator claimed that Wandayi's performance was questionable.