The Epsom candidates' debate last night drew out the bizarreness of a race where the frontrunner would rather lose and the ACT candidate is rallying behind the leader of another party. At least the unacknowledged presence in this race was finally discussed by name

It had all the fun a candidates debate should: ACT's John Banks said Pita Sharples and Tariana Turia - enemies on most policies - were high quality MPs and a great ad for MMP; Davia Parker said Labour should have introduced a capital gains tax when last in power, but was not brave enough; Paul Goldsmith said it was tough to be a man and wanted to be a man's MP; Green David Hay sang a Dear John letter to John Key and claimed the Greens had moved from "seriously radical to radically serious"; while Mana's Pat O'Dea declared he didn't want to win the seat because he'd had no idea how to serve people who earned $500,000 a year.

It was the Epsom candidates debate at Somervell Presbyterian in Remuera last night, which I chaired. There was some good policy discussed, with Parker pushing the importance of exports and Banks agreeing that we had to sell more - but also spend and borrow less. David Hay warned of peak oil and urged green jobs. Paul Goldsmith said National had a plan for tough times, but looking at my notes I couldn't tell you what it was.

But the reason Epsom has a profile like no other electorate isn't the policy, it's the politics and ACT's fight for survival.

So I pointed out that Goldsmith was ahead in the polls and asked if that made him happy... or not. He said he wanted to represent the people of Epsom, just how was up to them. But what did he want, I pushed. Did he want to win or not? He wanted what the people of Epsom wanted, he said.

It's hard to tell whether he feels dirty about the game he's being ordered to play. I guess he could always look into the audience to see Mark Thomas and take comfort from the fact that at least he's unlikely to be sacrificed by his leader in the way that Bolger sacrificed Thomas to Richard Prebble in Wellington Central in 1996.

John Banks has no qualms about the National-ACT deal that's defining the Epsom race; I guess he has no choice. I asked him why, when asked on Campbell Live what was the ACT brand, he replied "Brand Key". Why is ACT's brand based on the leader of another party and not his own leader?

He talked about John Key being the most successful politician in living memory and the like. Which still puzzles me, given that it was former ACT leader Rodney Hide who described National as a do-nothing government and ACT has numerous policy differences with National.

But that question opened up the other candidates. David Hay said "ACT used to be a party of principles. Now it's a party of convenience", made up of "National Party rejects and has-beens".

Pat O'Dea brought out an enormous - and it must be said, unflattering - photo of Don Brash, declaring that if Epsom backed ACT this would be their next MP. He derided Brash as dishonest, racist and past it.

At first Banks chose not to respond, saying he wouldn't honour such rubbish with a reply. But with his answer to the next question came something new: For the first time I can remember on this campaign Banks talked - and talked positively - about Don Brash.

Banks said the people of Epsom would expect him to respond to the "gratuitous attack" on Brash who was "a patriot", the best Reserve Bank governor the country's had and knew more about the economy than everyone in the room put together. He angrily removed O'Dea's photo from the front of the lecturn.

It was the tensest moment of the night.

What struck me afresh was the irony of ACT's predicament. The party of freedom is prisoner to National's whims; the party of individual responsibility is dependent on another for survival; the party of small government is relying on political welfare to get into parliament.

Yes, welfare. ACT is, frankly, a political beneficiary, unable to pull itself up by its own boot-straps and get parliamentary work in its own right. Even if Banks and maybe Brash make it into parliament, they will be beholden to National; a tool of the tories, but with little power to pull Key to the right. Banks will be to National what Jim Anderton became to Labour.

Worse, they'll spend three years justifying why they're in parliament at the taxpayers' expense when everything they stand for argues against that.

If any other party was in this position, ACT would be its fiercest critic. While there's nothing inherently wrong with tactical voting and considering coalitions before the election, the contradictions and hypocrisy here is a shame.

They're tied in knots and must know it. You'd expect the true libertarians and activists in ACT will pack up and set up camp elsewhere.

All of which is why Key is holding back his endorsement of this tormented game. We know he's given his stamp of approval thus far; he wants ACT to his right and the Maori Party to his left once more to absorb the fallout from National's more contentious plans. But he has to decide whether he wants to pay the political price of walking into this swamp.

Odds-on he will. Short-term pain for long-term gain. That's the sort of equation Key understands very well. But he'll want to do it late enough in the campaign that he doesn't give his opponents too much time to whack him about it, but not so late that it leaves a lasting impression on polling day.

Key will also be looking intently at the polls. The worst outcome for him is that he has the cup of tea, only for Banks to lose the seat thanks to those utterly turned off by ACT and Labour supporters voting for National.

It was a fascinating night and great to have around 130 people turn-out. And thanks to everyone at Somervell for the hard work organising the event.