That's the cruel truth that caught up with Rodney Hide this week, when he ' />

In the brutal world of coalition politics, it's all about the numbers.

That's the cruel truth that caught up with Rodney Hide this week, when he was toppled as the leader of the Act Party by a man who was not even a party member, much less a Member of Parliament.

The third caucus vote that rolled Hide was that of the disturbingly blurred Hilary Calvert (who may be less handsomely rewarded than she hopes when the party's list is compiled in a few months).

But the numbers stacked up that way because Hide had long lost the authority to lead. He was the perk-buster who took his fiancee to London on a taxpayer-funded holiday; the campaigner for transparency who connived in the cover-up of a colleague's grubby past; the buffed buffoon in a television dancing show who had been credibly criticised as a bully and led a caucus whose members were barely on speaking terms.

Brash was right to say Hide's brand had become toxic.

Those alarmed at the political resurrection of the former Leader of the Opposition seek to remind us of what they see as Brash's toxic past.

Certainly, he comes with baggage, but he's happy to display it: his agenda, unchanged since 2005, involves slashing public spending and when he speaks of delivering tax relief it is not the interests of the poor he has in mind.

But the reincarnated Brash is a different animal from the 2005 version. He is not seeking to be Prime Minister but the leader of a small, right-wing party that wants to, in his words, "give some spine" to its senior coalition partner in a National-led Government.

He does not need to carry the country with him; just more than 1 in 20 voters. And he will have a ready-made constituency of disaffected Act voters who have been desperate for some reason to return to the fold.

The scenario that is unfolding is such good news for the Key Government that it is not hard to imagine that National Party strategists had a hand in its design. Put simply, there is no downside for Key in what is happening. He can advance unpopular policies, such as asset sales, and use Act as his excuse.

A week ago Key was contemplating entering an election campaign with his only natural coalition ally doomed to extinction. And as his allies on the right melted down, storm clouds were gathering on the left. Hone Harawira's Mana Party, born in Auckland yesterday, poses a political threat to Key every bit as serious as the death of Act would have.

If Harawira wins in Te Tai Tokerau, he could bring a handful of MPs with him. If they and surviving Maori Party members do a deal with Labour, they could add up to numbers that would keep the Nats awake at night.

Key will give a nod and a wink to Act's candidate in Epsom - the electorate held by Hide and as good as promised to former Auckland mayor and National MP John Banks. But if things get tight, Key might need to consider doorknocking for Act.

Recent polling may translate into a seating plan that shows more than half the House to be blue, but the electorate has not come close under MMP to letting a major party govern alone and it's not about to start now. Before NZ First even turns the ignition key, it looks like being an interesting election.