And so Peters is a thorn in National's side.
Peter Dunne's gone. The Maori Party could support Labour, and that means National can only rely on David Seymour. And that's not enough to form a coalition.
So, if Peters takes a hit in the polls and some of his conservative voter base desert him, where would they go?
They'd go to the Nats. National would likely pick up their votes.
Peters has repaid the overpayment, plus an undisclosed sum of interest and possibly penalty fees.
He says he was paid the single person's benefit for seven years, apparently. And he has been living in a de facto relationship all that time.
So if that's the case, the error was made just before the last election. He's into his second election cycle while being overpaid by the ministry of social development. And for him to knowingly deceive the ministry as a high profile politician....well, he's a smart man. He's a lawyer. Why on earth would he take that risk for the sake of $60 a week?
I don't think this will stick, provided Peters is transparent. And he's not being transparent at the moment.
He is right to point out that this is a private matter but it's been leaked - and that's illegal - but it's been leaked and it's out there now and it's less then a month to the election.
He needs to reveal what he paid, how much interest, and if there were any penalties.
Otherwise this won't go away. And because Peters is tiptoeing around the issue, the public naturally assumes he has something to hide.
So will he take a hit in the polls?
We'll have to see how it unfolds in the coming days, but I don't think his voter base will desert him.
And then what happens? Well, whoever leaked this has poked the bear, haven't they?
Peters will have an idea about who did this and why, and if he continues to hold the balance of power come election day, how will that influence his decision about whether to swing left or right?
It's yet another extraordinary twist in this election.