To Labour's high command they are known as the killing fields. They are in London, along the M4 corridor, the north Kent coast, the south coast and the M11 corridor. They include lots of C1 (junior non-manual) and C2 voters (skilled manual). They are the voters who turned to Mrs Thatcher in 1979 and to Tony Blair in 1997.
Now Lord (Giles) Radice who wrote a famous pamphlet on southern discomfort in 1992 is warning that it is emerging in a new and more complex form. New Labour needs to win back families who have been hit by high interest rates, are concerned that taxes are not being wisely spent, and are worried by immigration and crime.
This crisis has sparked an ideological debate within New Labour. The left believes that Gordon Brown is siding with the Blairite modernisers. A fresh set of advisers have been brought into No.10 from the media, advertising and banking. His chief adviser, Stephen Carter, is portrayed by left opponents as the head of a 'Lib Dem cell' in Downing Street. Jennifer Moses, an American former Goldman Sachs banker who didn't notice when £1m went missing from her bank account worked for a Lib Dem-oriented think tank.
The modernisers want Gordon Brown to speed up public service reform and to address the perception that his government is uneasy with wealth and aspiration. Aspiration was used as an organising theme in the Queen's Speech, but events since then have served to undermine its resonance. Reforms to capital gains tax and action on non-doms affected few voters, but could be portrayed as anti-wealth and anti-enterprise.
Critics on the left say that the core vote is being neglected, while Hazel Blears has insisted that Labour has to be a party of the affluent as well as of the poor. In reality, Gordon Brown may welcome a row with the Labour left. He was as much a part of the New Labour project as Tony Blair and the ideological differences between them were very slim. But it suited him to play up the differences in the succession battle. There were big personality differences, of course, but the prime minister is less dour and more engaging on a one to one basis than he appears in public. He is very good at getting the information and ideas he needs out of someone very quickly.
Before the narrative of a foregone conclusion to the next election is pushed too far (notwithstanding Labour's very real southern vulnerability) it should be remembered that Dave Cameron is unlikely to be able to deliver much in the way of tax cuts. Indeed, shadow chief secretary Phil Hammond has warned that tax cuts could be the 'the great bonus of the second election'.
In 1979 James Callaghan, as a former naval NCO, noted that there was one of those great sea changes in British politics that produced Thatcherism. Another sea change in the mid 1990s led to the 'third way' of Tony Blair with its mix of social democracy and neo-liberalism tilted towards the latter. Another sea change could now be on the way, but the currents are more conflicting and turbulent than they appear on the surface.