A gathering at Britomart railway station this week gave a hint of the damage a Super City could do. One Labour MP was there, with a couple of Greens, several Auckland local-body members and a Super City mayoral candidate, Len Brown.

They were trying to revive the idea of a railway line under the CBD.

It was the presence of Labour that worried me. The Green Party is not powerful enough to do much damage to the national economy but Labour could.

The Labour Party would very much like Len Brown to win this election. Any party out of the limelight and facing a long spell at the wrong end of the wicket would seize this opportunity to put a score on the board.

If Brown wins this contest Phil Goff will be pouring his champagne, presuming Goff is still leading the party in October. Winning the Auckland supermayoralty would lift Labour's stocks, and his, considerably for next year's general election.

Commentators could no longer write their prospects off completely, they would be haunted by the fact that at the local elections Auckland went left.

Already the creation of a single Auckland mayoralty has attracted much more high-powered political participation than we have seen in a local election for a long time - at least on the left.

All potential left-leaning candidates bowed out for Brown and not even his televised breakdown in front of a Manukau council committee has caused any of them to break ranks.

So far the only splinter candidates coming into the race are on the right, where John Banks seems to be happily campaigning without much help from the National Party.

Right now Labour needs this new Auckland prize more than National. The question raised by the Britomart stunt is, have we created a terrible temptation for a major party of Government? The National Party will be in the same position one day.

It would be the easiest bribe in the world to promise a big city a glittering project at national expense. Who would turn down an underground railway if the Government was going to pay for it?

Labour deserves some credit here; at the Britomart gathering it did not, as far as I'm aware, give Brown any grounds for suggesting a vote for him could improve Auckland's prospect of an inner-city subway.

More important - since all candidates quickly endorsed the project - Labour has not committed its next Government to the cost.

But the fearful possibility remains. The mayoralty of greater Auckland will represent one third of the population of New Zealand. Representational power always needs to be checked by the need to raise all its revenue from those it represents.

But when Auckland speaks with its new single voice it will not necessarily be offering to pay for its desires.

A rail loop from Britomart to Newmarket, with stops in Wellesley St for the universities and Grafton for the hospital, may be so well patronised that it pays for itself.

It may increase the use of all the Auckland lines and bring more people back to the CBD. Alex Swney, head of the "Heart of the City" business group, was also at Britomart on Monday.

But if we Aucklanders really believed that, we would pay for it, just as we paid for the Harbour Bridge. We would support a mayor who proposed that we borrow the money in the confidence that the loan and operating costs would easily be covered by the tolls it would collect.

If we could be convinced it would pay we would buy a first-class railway - fast, flash and so frequent we never needed to look at a timetable. But that is not the sort of railway a Government would pay for, and nor should it.

A Government is entitled to suspect that if Auckland needs national taxpayers to pay for its trains it is because not that many Aucklanders are going to use them.

Back in the early 1950s when an exceptional Auckland mayor, Sir John Allum, was pressing the Government to approve loan finance for a harbour bridge, the city council was also asking for an electric railway to and around the CBD.

The difference was that Allum knew Auckland could and would pay for the bridge. Nobody could have the same confidence in a railway, even then, before motorways had reshaped the place.

Since then, Auckland civic planners have been announcing urban rail schemes so frequently that news editors cannot stifle a yawn. That will be why we haven't heard or read much about the gathering on Monday.

But it scared me. If a major party decides to buy the Auckland election with a promise of some uneconomic pork, it probably could. We have created a monster.