At Te Piiti Marae in Omanaia, Mr Harawira said the Maori Party was considering telling supporters to vote for Mr Davis - a day after John Key said he was comfortable with National supporters doing so.
"Things have just got real tough for me," Mr Harawira told the meeting.
"I've heard that the Maori Party is considering standing their man down and giving their votes to Labour's [Mr Davis] as well.
"So the fight for this seat has just become the kind I really like, which is us against the rest. I'm upset about it, because it's tough enough in Parliament on your own. I take it also as a bit of a compliment."
Maori Party candidate Te Hira Paenga said Mr Harawira's claim made little sense because his party could work with either Labour or National.
He said he was still telling voters to vote for him.
Maori Party co-leader Te Ururoa Flavell confirmed strategic voting had been discussed, as had the option of not standing a candidate.
"It's been a part of our strategy meetings for a while, but the official line is that Te Hira Paenga is standing as the candidate. We've endorsed him." But he was reluctant to say that he wanted supporters to vote for Mr Paenga.
"Everyone in the Tai Tokerau can make their own decisions."
The Electoral Commission confirmed it was too late to withdraw candidates.
Earlier, at a meeting in Moerewa, Mr Harawira was asked to justify his alliance with Kim Dotcom.
"The question for me was, 'How do I get more Mana MPs into Parliament?"' Mr Harawira said.
"I really hope Annette Sykes will win Waiariki, but if she doesn't, she's still going to come into Parliament."
He hinted that he would struggle through another term by himself, and having a team would bolster his influence and bargaining power.
"It's hard enough being a radical MP and activist, more difficult when you're on your own, and it would be nice to have at least a couple of mates."
Mr Davis was not aware of any strategy from either National or the Maori Party, and said he was after every vote he could get.
"I don't really care where they come from."
He did not agree that winning the seat would harm the left bloc overall.
"I think Kim Dotcom has harmed the left bloc because people are scared of him, swing voters we want to attract."