Former Machakos Senator Johnson Muthama was arrested during the Msambweni by-election on Tuesday for allegedly causing a disturbance.
Mr Muthama, who is Deputy President William Ruto’s ally, was apprehended at the Jomo Kenyatta Primary School polling station.
Former Mombasa Senator Hassan Omar confirmed the arrest, saying police officers took the senator from Kwale to Mombasa County.
“We are keeping vigilance because we know our opponents are bribing voters and can’t win this election fairly,” he claimed.
Police sources said Mr Muthama was taken to Port Police Station.
Mr Muthama, Mr Omar and former Kakamega Senator Boni Khalwale have been leading campaigns for independent candidate Feisal Bader.
Mr Bader’s team has alleged harassment by police officers while claiming that people in the Orange Democratic Movement (ODM) team are allowed to roam freely inside polling stations.