Frank Luntz justifies it with the following opening:
He then goes on to say that the focus group contains left-leaning voters from Manchester, presumably in order to discern whether they are any more likely to vote Conservative and hence form a path for the Tories to government.
"If you examine the election results from the last 50 year, the Conservatives could win the south, but still not win the election; Labour could take the north but not form the government; it's places like Manchester which make the difference (my emphasis)"
The problem with this is his opening statement is poppycock. As Mike Smithson points out on Political Betting:
For me the programme was a massive missed opportunity - Luntz cannot come cheap and these things are costly to set up and make (his emphasis). Yet they chose to hold amongst existing and wavering Labour supporters in Manchester where, we were told, all the participants came from. If the producers had checked they would have discovered that there’s not a seat in city in the list of the top 200 Conservative targets. The main action will be two LAB-LD scraps. In Withington Labour will be hoping to regain the seat lost last time and Manchester Gorton could go on an 8.25% swing. Surely they should have found a location more relevant to the CON-LAB battle?
Anthony Wells has also previously noted in an article from 2005 (reproduced in comment 160 of this Political Betting article - I cannot find the original)
The increasing geographical concentration of the Conservative vote is more of a problem, while boundaries changes mean that the number of seats in the South is increasing and falling in the North, the Tories cannot win with the South alone. At the next election the Conservatives are likely to need about 115 seats to gain a majority - on my current calculations only 47 or so of their most winnable seats will be in the South East, South West, London or Eastern regions. The regions with the most target seats will likely be the North-West and West Midlands, both regions where the Tories went backwards at the election. The Conservatives cannot win without turning round their position in the North. While the undeniable fact that the Conservatives are irrelevant in many of the major cities - Manchester, Sheffield and Liverpool for example - is not a great problem, the Conservatives can easily win without any MPs in these cities, they do need urban seats in places like Birmingham, Bolton, Leeds and Dudley.To further back this up, a recent survey of marginal seats did not hold one poll in the Manchester area.
The reality is that it is nonsense to suggest, as many media outlets including the BBC and ITV do, that Manchester is an important target for the Conservatives at the next election. I assume when political journalists for these organisations hear the word "North", they automatically default to the only place in t'North they know - Manchester - and claim that it then becomes an important battleground for the Tories. The reality is that Manchester, politically at least, is irrelevent to who will form the next government.
Which makes it even more puzzling why Labour are holding so many of their conferences in there. In 2006, they decided to move away from Blackpool to host their conference in the city, followed up this year and they plan to be there again in 2010. Presumably the excellent conference facilities are the main reason they are holding so many conferences there, but one cannot help feeling they are missing a trick. In the US for example, the Democrats recent conference venue in Denver, Colorado and the Republicans venue of St Pauls-Minneapolis, Minnesota were picked due to their importance as swing states. Although the political map has changed somewhat from when these venues were chosen, with Minnesotta and nearby target Wisconsin looking like solid Democratic territory in 2008, the Democrats choice of Denver looks set to carve a path to the White House using current opinion polls; wins for Barack Obama in the Kerry states plus Iowa, Colorado and nearby New Mexico give him 273 electoral votes, three more than the 270 required.
The Conservatives will also be hosting their conference in the Manchester next year. If Anthony Wells above is to be believed, Leeds might have been a more sensible choice provided they could find a conference facility in the region up to the required standard.