At a time of global disaffection with establishment politics, one national leader who appears to have bucked the trend is New Zealand Prime Minister John Key. After six years in the job, polls continue to show Key with personal approval poll ratings well into the 50s, and it appears all but certain that his hold on the job will continue after his government faces voters tomorrow.

Despite that, Key doesn’t seem to have much luck with election campaigns. Both now and in his first bid for re-election in 2011, Key and his conservative National Party entered the campaign with high hopes of achieving the holy grail of New Zealand politics — an absolute parliamentary majority under the country’s proportional representation electoral system — only to encounter serious bumps on the road to polling day.

The problem last time around was the “teapot tape scandal“, involving a recording of a private conversation in which Key reportedly disparaged the ageing support base of the New Zealand First Party, which was said to be “dying off”.

This time, things got weird. Edward Snowden, Julian Assange, death threats and leaks all threatened to derail Key’s campaign — and that’s before rapper Eminem got involved.

While it’s entirely possible that the stars might still align for the National Party, it’s at least as likely that it will once again emerge from the election searching for coalition partners. As such, a large part of the story of the election will be the performance of minor parties, with much depending on their ability to cross the 5% threshold that entitles them to seats proportionate to their share of the national vote.

The hurdle the National Party must clear is a majority not of the overall national vote, but that share of it scored by parties that win parliamentary representation. The more of the vote goes to minor parties that fail to do so, the easier that becomes.

However, a familiar-looking downturn in support for the major parties has shortened the odds that minor parties will once again hold the balance of power. The main beneficiary has been the aforementioned New Zealand First, whose supporters have proved livelier than Key purportedly foreshadowed. The party fell below the threshold in 2008, but it bounced back again in 2011 to elect a fresh retinue of eight MPs. For most of the last parliamentary term it looked at grave risk of going under again, but a surge in support during the campaign period appears to have put that notion to rest.

New Zealand First is the creation of maverick political veteran Winston Peters, who founded it in 1993 after splitting from the National Party. It has invariably backed the party in the stronger parliamentary position to govern, and has been equally consistent in making life extremely difficult for whoever it has been partnered with. The National Party performed strongly enough in 2008 and 2011 that it was able to rely on less troublesome allies, but it would not need to go too far backwards for that to change after tomorrow.

A potential alternative partner is the Conservative Party, which was founded by millionaire property manager Colin Craig to oppose such causes as same-sex marriage and the country’s anti-smacking law. Craig is making a run for the Auckland electorate of East Coast Bays, which if successful will entitle his party to further seats even if it doesn’t clear the threshold. However, the odds appear to be against it achieving either goal, despite a lift in support on the back of National’s troubles during the campaign.

The other minor party wild card going into the election was Kim Dotcom, the mastermind behind file sharing websites Megaupload and Mega, whom The Economist describes as “an internet entrepreneur or hacker (take your pick)”. As a German-Finnish citizen, Dotcom is barred from running for office, but it appeared that his Internet Party might gain traction thanks to his financial muscle, populist policies, peculiar joint-ticket arrangement with the Maori rights outfit the Mana Party, and an enviable talent for garnering publicity — most recently exhibited through Monday’s “Moment of Truth” event involving Snowden and Assange, which doubled as a rally for his party. However, polls have provided little indication that voters are responding to his campaign in large numbers.

As for Labour, leader David Cunliffe had a brief moment of glory when he was overwhelmingly rated the better performer in the first of four leaders debates. However, this singularly failed to reverse the alarming decline in his party’s poll ratings which began at the start of the year, and still doesn’t seem to have bottomed out.

Together with its natural coalition partners in the Green Party, Labour looks set to enter post-election horse trading with at best 50 seats out of 120, with only a handful of further seats likely to be held by players who would sooner favour doing business with them over an ascendant National Party.