OPINION: Twelve years ago Simon Bridges and Winston Peters had their first run-in.

Peters was attempting to regain his old seat of Tauranga, the once-loyal electorate he had used to launch his own political party back in the early 1990s. Bridges was looking to launch his political career off the back of winning the seat.

He managed it, beating Peters back by a large margin and sending NZ First packing from Parliament, as its vote had also cratered below 5 per cent. Both were magnanimous, Bridges paying respect to the political legend and Peters congratulating the "bright young guy".

Neville Marriner Simon Bridges with John Key in Tauranga in 2008 - when he first ran into Peters, who John Key had ruled out working with.

Such kindness seems quaint now. Peters has spent the last two years mocking Bridges as a leader constantly on the verge of being rolled. Bridges has held back until Sunday, when he delivered what he will hope is a knockout punch: ruling NZ First out of any governing arrangement with National after the 2020 election.

This sets the stage for an all-out war of an election that will be the end of either man's political career.

GETTY IMAGES: COMPOSITE National leader Simon Bridges has ruled out working with Winston Peters and NZ First after the 2020 general election.

There is very little chance that should NZ First return to Parliament after the election National would have the numbers to govern without them. That's only happened in 2011 and 2014, when Labour was so weak NZ First could soak up some of their opposition vote - Labour is simply much stronger now. So if NZ First come back over the 5 per cent threshold National will face another term out in the cold, and Bridges will be toast.

On the other hand, if National is successful in forcing NZ First out of Parliament it's unlikely Winston Peters will find his way back in. He's come back from Parliamentary defeat twice before in 1984 and 2011 - but Peters will be 78 in Election 2023. Third time might not be the charm.

All of this means that it is imperative for Bridges to utterly rout NZ First this September.

There's a pleasing simplicity for National in deciding to go all out against all three parties in Government. You don't have to moderate your message against some ministers while attacking others: you just attack them all. The party will be hoping the NZ First voters who wanted the party to go with National are able to be convinced to switch their vote altogether.

It also satisfies a clear desire for utu for National, who still can't really believe Peters was filing a lawsuit against several of them while also negotiating with them at the last election. (Some also still don't really believe that it was actually honourable for NZ First to go with Labour as they were not the largest party.)

There's also a general very first-past-the-post feeling among National MPs that as the natural party of government the kinds of compromises Labour has to make for NZ First are simply not tenable for National.

The decision by Bridges mirrors one made by Key in 2008 and 2011. Key made his decision from a position of much more strength however, with a lot more opinion polls showing a clear path to victory without NZ First. Bridges has two 1 News/Colmar Brunton polls showing the same recently and presumably some pretty good private polling.

The strategy for NZ First is clear and has already been made by MP Mark Patterson on Twitter - vote for us as the only chance of stopping an ultra-left Labour-Green government. This strategy only works if a Labour/Green government seems inevitable.

Herein lies the risk for Bridges. If voters don't think National have a shot of it alone the party's support could drop a lot further as right-wing voters decide they want to vote for NZ First as a handbrake on Labour and the Greens. It will be polling that sets that narrative - and given the trouble media is in right now we are probably looking at an election with less public polls than ever before, so things could get quite chaotic.

Game on.