County returning officer Erastus Otieno said Awiti won with 46,346 votes against Kasipul MP Oyugi Magwanga's 14,661.
Residents were up in arms as they shouted that they will support Jubilee party leader Uhuru Kenyatta in August.
On Monday evening, Magwanga was commanding an early lead against the incumbent, hence the protests.
"This is clearly rigging. We will not agree. We will vote President Uhuru Kenyatta in August. Awiti has not done anything," one of the protesters said.
The group said they expected Magwanga to win on grounds that the governor has failed on matters development.
The residents engaged the police in running battles after the results were declared.
Otieno accused constituency party officials of holding them at ransom after they delayed to submit some of the results.
"We cannot wait any longer for constituency officials who don't want to hand in what they have."
"We, therefore, have to release the results we have," Otieno said.
Otieno, who was accompanied by the county election board chairman Tom Cheriga, refused to explain how they came up with the results.
"Anxiety is high in the county about who got what after the nominations."
