A big group of Green Party supporters voting for National's Paula Bennett in Waitakere effectively cost Labour's Carmel Sepuloni the chance of winning the seat.
But Labour MP Damien O'Connor has both the Greens and National Party voters to thank for his victory in West Coast-Tasman.
Statistics on split voting in the general election show that half of the 3308 Green Party voters in Waitakere ticked Ms Sepuloni but 13 per cent voted for Ms Bennett - the 429 votes more than enough to give her the win.
Ms Bennett only just held on to the seat with a majority of nine after a judicial recount.
That was higher than in 2008, when Ms Bennett got the support of 9 per cent of the Green voters.
The Green Party candidates made it clear in marginal electorates that they were campaigning only for the party vote - an indication supporters should give Labour their candidate votes. That message was picked up by some.
In West Coast-Tasman, Mr O'Connor won back the seat from National's Chris Auchinvole with support from two-thirds of the Green supporters. Their 3074 votes totalled more than his majority of 2539.
Mr O'Connor also picked up a sizeable chunk of National Party voters, getting a further 2468 votes from the 16 per cent of National voters who chose him as their local candidate over Mr Auchinvole.
In Auckland Central, 63 per cent of the 7797 Green voters voted for Labour's Jacinda Ardern and in New Plymouth 60 per cent voted for Andrew Little, although they both missed out on the seats.
Tactical voting was particularly high in the Epsom electorate - both on the left and the right. However, it was with a twist, as left-wing voters cast their votes for National's candidate to try to edge out Act's John Banks.
More than half of the Green Party voters (54 per cent) and 35 per cent of Labour voters voted for National candidate Paul Goldsmith - a total of 4417 votes.
By comparison, in 2008, National's candidate Richard Worth was backed by 11 per cent of Labour voters and 18 per cent of Green voters.
The deal between National and Act to ensure Act's survival meant Epsom was the most controversial electorate battle, including the now infamous cup of tea between John Key and John Banks. That was seen as a nod for National voters to vote for Mr Banks.
The statistics showed it worked - 60 per cent of the 23,725 National Party voters voted for John Banks. However, that was lower than in 2008, when 70 per cent of National supporters voted for Rodney Hide, who was then Act's leader.
One in five of the Act voters in the electorate either could not stomach the deal or objected to the rolling of Mr Hide. Only 80 per cent of Epsom's 939 Act voters chose Mr Banks and 14 per cent voted for Mr Goldsmith instead. The number of Act supporters in the electorate had also slumped, from 2389 in 2008 to 939 in 2011.