NZ Herald gets it wrong
This is a common, but serious, mistake. The NZ Herald has written about the alleged over-spending in Tauranga and refers to the Creech-Boorman electoral petition where Creech replaced Boorman in Wairarapa in 1988.
The Herald states that Creech was declared elected because Boorman had broken the spending limits. This is incorrect. Creech was declared elected because the electoral court found he got more votes than Boorman. Yes Boorman was also found guilty of over spending which invalidated his own personal vote for himself, but that would merely have seen a by-election if it were not for the fact that the Court also found that Creech won more votes after it ruled on some disputed ones.
So (and I have checked this out) if Clarkson wins and is found to have over-spent (something strongly denied, and as far as I am aware verified by lawyers), then this does not elect Peters, but merely voids the election and a by-election would be held.
And if NZ First did not make 5% and had dropped out of Parliament, but Peters won the subsequent by-election, this would not qualify them for any List MPs.