Mrs Katene (53), a mother of five, won the party nomination for Te Tai Tonga, which is the country's largest electorate, after the unexpected death of candidate Monte Ohia (62) in June.
She was named yesterday as No 7 on the party's candidate list.
Mrs Katene was confident of beating Mr Okeroa for the seat, which takes in the South Island and Wellington.
"The plan is to win Te Tai Tonga and give the people an independent voice," she said.
"What we have at the moment [in Parliament] is a party voice."
A Wellington-based lawyer, Mrs Katene has been travelling around the electorate for the past three weeks, and was pleased with the results of the latest Marae DigiPoll, showing her ahead of Mr Okeroa 42.4% to 39.4%.
A three-term MP, Mr Okeroa said the polls showed he was better placed than in previous elections.
He warned the sheer size of the Te Tai Tonga electorate meant candidates faced enormous financial pressures as they hit the campaign trail.
"I was just about bankrupted the first time."
While the Maori Party was preparing for a roadshow around the country in the coming weeks, Mr Okeroa said, "I am my own road show."
"My roadshow doesn't stop . . . it just continues," he said.
Confident of winning his seat, Mr Okeroa said he was also campaigning for the party vote but conceded the Maori Party represented "a huge challenge".
Both Te Tai Tonga hopefuls said the cost of living was shaping up as a key campaign issue this election.
