Two quite different "cities" are coming together in the new Auckland - and whoever wins today's mayoral election will be elected by only one of them. Legally, of course, four cities and three districts are merging into the new Auckland Council.

But in social and political terms, there is a stark divide somewhere around the narrowest point of the isthmus at Portage Rd in Otahuhu, where the Tainui canoe was famously carried across from the Otahuhu Creek to the Manukau Harbour.

South of that line, the Herald's "mood of the city" sampling of 300 people last month found overwhelming support for Len Brown with 69 per cent of decided voters against just 22 per cent for John Banks.

North of that line Banks was ahead, by 52 per cent to 36 per cent.

The division is partly socio-economic. The last Herald DigiPoll showed Brown ahead among households earning up to $80,000 a year and Banks ahead above that.

The mood of the city survey found Brown massively popular with Maori (87 per cent of decided voters) and Pacific people (69 per cent), with Banks marginally ahead among Europeans and Asians.

"A leader will look after not only the high class, he will come down and help the low class," said Misi Toumoua, 55, a Brown-voting artist who sells pillows at the Otara market.

Conversely, Malcolm Beattie, chief executive of an international sports travel company and former long-time head of the Auckland Rescue Helicopter Trust, is voting for Banks because he's " a successful businessman".

"Commercially he's savvy," he says.

But unlike national elections, when socio-economic status dominates voting, the Super City polling indicates a geographic overlay on top of the traditional pattern, showing that Aucklanders do not yet think as one city.

In the south, Brown is almost as popular among property-owners (67 per cent) as he is among renters (73 per cent). He is well ahead of Banks even in the middle-class Howick ward.

"He's the one for Manukau, I suppose," said Dannemora accounts clerk Carla Moore, 27.

Conversely north of Portage Rd, Banks' support is virtually the same among both renters (51 per cent) and homeowners (53 per cent). In the Herald surveys he was well ahead on his home turf in Auckland City and north of the harbour, and was in a close race with Brown in Waitakere.

"I heard John Banks was good, that's the only name I recognise," said Sandringham mother Linda Taihia, 26.

The challenge for whoever wins today, therefore, will be to reach out to the other "city" that voted against him - and somehow meld the two cities into one.

This will be partly a matter of building an inclusive team. Veteran political scientist Graham Bush notes that the Super City legislation gives the new mayor powers to choose the deputy mayor, create a committee structure and choose all the committee chairs.

"It's important that the mayor uses his prerogative to appoint the deputy mayor and council chairs to not have all the committee chairs from, say, Auckland City and the North Shore," he says.

He says leftist Auckland Regional Council chairman Mike Lee has shown how to do it, reaching across the political divide to make Auckland Chamber of Commerce chief executive Michael Barnett his deputy in 2007.

Depending on who is elected to the new Auckland Council, that could mean Brown giving the deputy's job to someone like outgoing Rodney mayor Penny Webster, a former Act MP, or Banks picking a southern deputy such as Sir John Walker or Franklin's Des Morrison, a Maori former steelworker.

Barnett, who had to drop off the Citizens and Ratepayers ticket this year because of cancer, says "the worst thing" Brown could do, if he wins the mayoralty, would be to treat what may be a sizeable C & R minority as an "Opposition".

"I can see Len Brown being capable of sitting down with a mix of Right and Left and being able to work with them," Barnett says.

Ethnically, the Pacific majority of voters in the two-seat Manukau ward and C & R's selections in some other wards should ensure at least a handful of brown faces in the new lineup, although there is no guarantee that any of the Asian candidates will make it.

But the new mayor will also need to give some real power to three new boards - a Maori board chosen by the original tribes of the isthmus, and Pacific and ethnic boards to be chosen by the mayor.

Chinese community leader Professor Manying Ip says the boards will be no use if they can only rubber-stamp decisions made elsewhere.

Te Runanga o Ngati Whatua head Naida Glavish says Maori still want Maori seats on the Auckland Council itself. Brown said in the campaign that he also wants Maori seats, although he told one meeting: "I'm one vote on this, it will be a democratic process that I want us to go through with the whole of the community."

But building an inclusive team is only a first step. Barnett says building a successful single Super City requires a much harder project - bringing the south's marginalised communities into the mainstream world economy.

Tony Mayow of the Auckland Community Development Alliance, a coalition of social service groups set up in response to the Super City, organised protests against the change only a few months ago - but now sees the new council as an opportunity to tackle areas of deprivation.

"If we are actually going to build an internationally competitive city, then we have to have a society within that city that attracts people to it," he says. "You cannot operate a two-city model, that's just never going to work."

Of course every large city in the world has rich areas and poor areas. But, just as New Zealand has become one of the most unequal developed countries in the past quarter-century, so Auckland's social divide has become a yawning gulf.

Research done for the Royal Commission on Auckland Governance found the region has more than its fair share of both rich decile 10 and poor decile 1 schools, with relatively few in the middle. More than half of all students in decile 1 schools are in Auckland.

Babies are now twice as likely to die before their first birthday if they are born in Manukau (6.8 out of every 1000) than if they are born in Rodney (3.4).

Around a fifth of all working-aged adults were on welfare benefits in June in Manukau (17 per cent) and Papakura (22 per cent), with the highest numbers on the domestic purposes benefit. On the North Shore only 7 per cent were on benefits.

Almost two out of every five working-aged Maori, and almost one in four Pacific people, are on welfare across the region, compared with only 9 per cent of Europeans and Asians. More than half of all working-aged Maori in Papakura are on welfare.

"That sort of polarisation is what Auckland is," says Barnett. "It needs to change."

In the 2006 census, 24 per cent of the region's under-15-year-olds were Pacific children, 18 per cent were Maori and another 18 per cent were Asian.

Barnett says our economic prosperity depends on helping those children through education into good jobs.

"This is not just a social issue. This is an economic development issue," he says.

He points to huge sums already being spent in South Auckland by multiple state agencies, state-subsidised charities and local councils. He hopes the Super City will lead a "whole of government" effort to focus that spending on education and helping young people into training, work experience and jobs.

"We need to provide incentives for young people, incentives for employers to employ them," he says.

"This is not something that you're going to be able to go out and get some quick runs on. It's a long game."