How vote splitting shaped the electoral map

The Maori Party's demise appears to be down to a deal between Mana and the Maori Party backfiring and working in Labour's favour rather than bolstering Maori Party co-leader Te Ururoa Flavell's chances of holding his seat.

The Mana Party and Maori Party had decided not to stand against each other in the Maori seats to try to maximise their votes.

However, on election day a significant number of Labour voters who had supported former Mana candidate Annette Sykes in Waiariki in 2014 instead went back to Labour and many of the 2500 former Mana voters also backed Labour instead of the Maori Party - enough to push Tamati Coffey ahead of Flavell.

Reports on voters who split their votes show that Maori Party co-leader Te Ururoa Flavell got a slightly higher proportion of votes from Labour voters than in 2014 - 26 per cent up from 25 per cent.

However, in 2014 20 per cent of Labour Party voters had supported Mana's Sykes - and in 2017 the vast bulk of those backed Coffey instead of Flavell after Mana opted not to stand.

Nor was Flavell able to pick up any of the former Mana Party voters after its vote collapsed from 2500 to 270.

The Maori Party picked up none of that and its vote also dropped slightly by about 100 votes while Labour's soared by 5,500.

In 2014, Labour's candidate Rawiri Waititi got support from only half of Labour voters in the seat. In 2017, Coffey got support from 70 per cent of them.

In a piece on the Spinoff, Coffey's campaign chair Hayden Marriner described the agreement between Mana and Maori as an "own goal" and said Labour's strategy had been to convince Labour voters to back Coffey instead of splitting the vote - and to target the Mana voters of 2014. That worked.

It was a different story in Te Tai Hauauru where Maori Party candidate Howie Tamati picked up much more support from Labour voters than the Maori Party's 2014 candidate had done - but while he got within about 1000 votes of reclaiming the seat it was not quite enough to unseat Labour's Adrian Rurawhe. Tamati got 24 per cent support from Labour voters, while Rurawhe's dropped from 68 per cent in 2014 to 60 per cent this time.

Across all electorates, National Party voters were the least inclined to split their votes. Fourteen per cent voted for a candidate from another party compared to 23 per cent of Labour voters and two thirds of Green Party voters. Labour was the biggest winner from the Green Party voters - just over half of Green voters voted for a Labour candidate.

The most confused result was in Nelson where the Green Party's Matt Lawrey was campaigning strongly for the electorate vote to try to win it from National's Nick Smith.

Both Labour and the Greens refused to give way or cut a deal - and the confusion resulted in almost 20 per cent of the Greens' voters voting for Labour's Rachel Boyack while 30 per cent of Labour's voters voted for Lawrey. NZ First voters were also split between Lawrey and Boyack and even National voters joined in the fun - six per cent voted for Lawrey and three per cent for Boyack.

As a result, Smith held the seat, albeit with a reduced majority.

In what is perhaps a reflection of the difficulty NZ First had in choosing between National and Labour, NZ First voters were almost evenly split - 22 per cent of the party's voters voted for a National Party candidate and 24 per cent voted for a Labour Party candidate.

Seats in which National Party voters did split their votes included Epsom where 62 per cent voted for Act's David Seymour and Northland where 20 per cent (3627 voters) voted for NZ First leader Winston Peters, who lost the seat to National's candidate Matt King. Peters also got support from a third of Labour voters in that seat - about 4150 votes.

Vote splitting was also fairly common in Whangarei where NZ First MP Shane Jones got support from 17 per cent of Labour voters and seven per cent of National voters. However, he was unable to convince more than 65 per cent of New Zealand First voters to back him - about 20 per cent gave their votes to National's Shane Reti instead. By comparison, Peters secured 91 per cent of NZ First voters in Northland.

In Ohariu where United Future's Peter Dunne pulled out less than four weeks before the election, most National voters were quick to back National's Brett Hudson instead - but 10 per cent voted for Labour's Greg O'Connor. That combined with most Labour voters and almost two thirds of the Greens' voters saw O'Connor take the seat.