Poll of Polls: Coalition has a way to go

Just how far the newly minted Labour-Green coalition-in-waiting has to go is underlined in RNZ's Poll of Polls.

National's lead over the combined Labour-Green total in the average of the four polls through May was 4.7 percent.

But there is some hope for the newly-weds.

First, only part of the last poll in the four-poll average, TV One's, aired on Tuesday night (7 June), was taken after the two parties' 31 May 'memorandum of understanding'. The full effect, if any, of the join-up will show up only after some time.

Second, the trend since January has been towards a lower National lead over the joined-up pair - to a bit under 3% by the end of May. If this trend continues, the combined Labour-plus-Greens score will head National by the end of 2016, well before the next election, due by October 2017.

But the chart also shows that trends can reverse. A nine-month trend towards Labour-plus-Greens from the 2014 election put National briefly behind in mid-2015. But that trend reversed over the next six months into a healthy National lead.

Moreover, National's average through this year has been between 44% and 48%, remarkably high for the midyear of a third term in government.

Still, the long-term trend since the 2014 election is towards the break-even line.

Much depends on whether Labour can dig itself out of its pit. Through this year it has sat around or a bit below 30%, dipping to 28.1% in April. Unless it can add at least 5 percentage points by the 2017 election, the government-in-waiting it hopes it has formed with the Greens may well still be waiting in 2018.

The Greens have maintained an average of around 12% through this year, hitting a high of 13.2% when Labour hit its low. That raises another question: can either of the partners lift its support by bringing in new support from National or New Zealand First or the non-vote? Or will they cannibalise each other?

New Zealand First has held its support close to 10% through this year, up from 7%-8% through 2015. That has reversed the usual non-election-year smaller-party fade. New Zealand First has joined the Greens as an established - fourth - party.

ACT and the Maori Party have each hovered around 1% through the year. United Future has been just above or at zero.

* The poll-of-polls is an arithmetical average of the four most recent major polls from among: TV One Colmar Brunton, TV3 Reid Research, NZ Herald DigiPoll (discontinued since late 2015), Roy Morgan New Zealand and the unpublished UMR Research. The four polls in the most recent average were, in order of interviewing, Morgan (October), TV3, UMR, and TV One (all in May). The first point on the charts is the actual 2014 election result. Only Roy Morgan and UMR have polled in every month throughout the period, so the average is overweighted with those two. The Fairfax Ipsos poll, which was in the 2011-14 averages, has not polled since the 2014 election.