ODM leader Raila Odinga has told Migori County residents to vote for the party's candidate Ochillo Ayacko, terming other aspirants imposters.
At campaign rallies where Deputy President William Ruto became a target again, Mr Odinga urged his supporters to show loyalty by voting for the party's candidate in the October 8 by-election.
Mr Odinga, who addressed the crowds by the phone, said Mr Ayacko, a former minister in the Kibaki government, believes in the Orange party ideologies and asked Migori people to vote for him.
The by-election was necessitated by the death of Senator Ben Oluoch on June 19.
At a rally in God Jope, residents of Suna East Sub-County were addressed by Mr Odinga on a loudspeaker through their MP Junet Mohamed's phone.
Mr Odinga, who spoke in Dholuo, told voters to ignore his critics and remain united behind Mr Ayacko and his handshake with President Uhuru Kenyatta.
"I am appealing to you to vote for Ochillo Ayacko as the senator because he is the best candidate. Come out in large numbers on October 8 and stand with ODM," said Mr Odinga.
"Believe in the handshake as it is going to take this country to the next level. I will be coming on Thursday and Friday to tell you more," added Mr Odinga.
Mr Odinga is scheduled to be in Migori on Thursday and Friday to campaign for Mr Ayacko.
Politicians at the rally hit out at Deputy President William Ruto over his remarks that Mr Odinga was using the handshake with President Kenyatta for his selfish motives.
"We are telling the DP to shut up and let our party leader be. He has made our party leader a punching bag, hurling insults at him at every turn. We are telling the DP loud and clear to respect Mr Odinga because he is not his equal," said Mombasa Governor Hassan Joho.
He also dragged Mr Ruto into the Migori campaigns, claiming the Federal Party of Kenya candidate, Mr Eddy Oketch, was sponsored by the DP.
"Let us not allow Mr Ruto to upset Mr Odinga's support base. All of you should remain united behind Mr Ayacko," said the Mombasa county boss.
Mr Ayacko is facing stiff competition from Mr Oketch who is backed by Migori Governor Okoth Obado, who is currently detained over the murder of university student Sharon Otieno.
Mr Obado enjoys wide support in the county.
Mr Joho and Suna East MP Junet Mohamed led the ODM campaigns in Nyatike and Migori towns.
"On Monday next week, we are appealing to you to turn up in large numbers and vote for Mr Ayacko to represent you in the Senate," Mr Joho told Nyatike residents.
Nyatike MP Tom Odege told the residents to come out in large numbers and demonstrate their loyalty to Mr Odinga on polling day.
While speaking at the Coast on Sunday, the DP accused Mr Odinga of political conmanship and blamed his exit from ODM on the ODM leader.
ODM politicians Monday hit back, for the second time in as many days.
Mr Mohamed said: "Ruto should stop blaming our party leader for his woes. He has been hopping from party to party, has Raila been the reason behind it? Let him leave Jubilee quietly for we know that is what he is planning. He should not bring Raila into it."
The ODM politicians asked the DP to stop making outrageous accusations against Mr Odinga.
Mr Oketch Monday pitched tent in Rongo and Awendo sub-counties. He urged his supporters to turn up in big numbers and vote for him.
Others in the race are Mr Peter Jobando (Green Congress Party), Mr Samwel Otieno (Independent) and Mr Dickson Ogolla (Independent). Mr Solomon Hodo of People's Democratic Party withdrew from the race and backed Mr Oketch.
Migori County has 388,000 registered voters spread out in the eight sub-counties.
The competition has become so stiff that ODM has deployed troops in the region for the past one week. And Mr Odinga is expected to camp in the area for two days.