Paths to victory: How Simon Bridges could become PM, and what might keep Jacinda Ardern in power

Jacinda Ardern's popularity worldwide won't necessarily help her overcome Labour's perceived inability to fulfil its promises at home and win this year's election, it's been claimed.

But National's Simon Bridges has perhaps bigger obstacles to overcome if he wants to unseat her as Prime Minister, University of Waikato policy and international relations expert Al Gillespie told Magic Talk on Friday.

"They're probably viewed much better internationally than they are domestically," Dr Gillespie said of the Labour-NZ First coalition.

"Internationally, the reputation of the Government - and especially the Prime Minister - is very high. How that will translate at home, I'm not sure."

In addition to her widely-praised response to the Christchurch terror attack, Ardern has made headlines overseas for climate change advocacy. Public Service Association national secretary Glenn Barclay says a recent poll of its 75,000 members found climate change was "right up there" in terms of importance.

And that was before Australia caught on fire.

"I think the bushfires will alter things," he told told Magic Talk. "We had the climate strikes last year which generated a lot of interest and activity, but I think these bushfires will have changed things."

While that would suggest a swing towards the Government and against National - which has traditionally been less eager to take action on stemming climate change - Dr Gillespie says many New Zealanders see little difference between the two camps.

Al Gillespie.
Al Gillespie. Photo credit: File

And with Bridges taking the party "much more towards a centre position", Dr Gillespie says it's opened up the possibility of a potential coalition with the Greens.

"You need to be much more fluid in the boundaries between the parties. He clearly can't do it by himself, so he needs to be willing to talk to whoever he needs to, to get those numbers."

But there's a big problem. Green Party co-leader James Shaw told Newshub Nation last year they'd "never" do a deal with National as long as Bridges was leader. In contrast, he briefly held the door open for Bridges' predecessor Bill English.

Though it voted for the Climate Change Response (Zero Carbon) Amendment Bill, National has also promised to undo the Government's fossil fuel drilling ban, and its ally ACT has criticised new climate change teaching resources as "state-organised bullying of kids".

Winston - king or queenmaker? 

National's poll ratings have been higher than Labour's through most of the Government's term, and it got more votes at the election in 2017. But NZ First leader Winston Peters sided with Labour, and with relations between Peters and his former party deteriorating since then, National faces yet again winning the popular vote but failing to form the Government - unless it or far-right minor party ACT can significantly increase their share. 

In a column for NZME on Friday, right-leaning political commentator Matthew Hooton points out that no minor party that's entered into a coalition agreement has ever reached the 5 percent threshold at the following election. 

"For Peters to be more than a quirky footnote, he needs to break that rule in 2020," Hooton wrote. "The same holds for the Greens."

Simon Bridges and Winston Peters.
Simon Bridges and Winston Peters. Photo credit: Getty

If NZ First doesn't make the threshold, without an electorate seat to fall back on they'll be knocked out of Parliament, just like in 2008 after then-National leader Sir John Key ruled out working with them.

"There is still the possibility that Labour and the Greens together might form a Government without NZ First if they get the votes," said Barclay. "If NZ First doesn't get across the line then that raises the possibility of a National-ACT Government."

But Barclay said Bridges would be "crazy" to rule out Peters, with the left and right voting blocs looking stable and unlikely to shift enough to give National and ACT an outright majority. 

After Labour took power in 1999, National's vote collapsed to below 21 percent at the following election. Barclay believes that didn't happen this time because supporters feel they were wrongly denied in 2017.

"2017 was the first MMP election where the largest party didn't form the Government. This was always going to be in my mind a test of MMP, and I think we've come through that okay. 

"There is acceptance the Government was validly formed, but there remains a perception among some people that National wasn't properly defeated either, which has meant their vote has held up pretty stable through the period of this Government."

Bridges last year said he'd be "very, very clear" who National could work with when 2020 rolled around. He declined to comment when asked by Newshub on Friday.

Dr Gillespie said Bridges had done well to keep the party within shot of victory.

"He's come to grips with a very difficult agenda - all the things that are going on right now are often unprecedented, and he's had to modify the party. He's made calls which have been difficult for the grassroots of the party."

Labour's biggest weakness

Barclay said "overpromising" has been a constant problem for Labour, which has been criticised for failing to significantly reduce child poverty, backing down on its proposal for a capital gains tax and forced to rework significant election promises like KiwiBuild.

In a recent post on social media, the National Party also claimed the Government had failed its promises on light rail, more police and more early childhood education services, 

"They've committed themselves to limits on Government debt and expenditure as a proportion of GDP, and that has held them back in their ability to really fundamentally attack some of these issues."

Barclay said it's also been slow to move on reforming welfare, with the vast majority of the Welfare Working Group's recommendations rejected.

"I would like to see them move on that more quickly than they are at the moment. But we are yet to see what their full response to that will be." 

The election is expected to be held in late September, and no later than November.