Are you really saying that the Tory party has given up trying to get the support of Brixtonians denounced elsewhere on these boards as "gentrifiers" - people in IT, media and advertising jobs with household incomes in the 70k-120k range. If the Tories have given up on higher rate taxpayers and mortgage holders who are you looking for as a core vote?
And until very recently, I would have thought there was a not insignificant conservative vote from middle-aged black churchgoers.
Going solely on the demographic changes across the constituency in the last five years - largely driven by the property market - the Tories ought to have seen a
rise in their vote! Anyone who looks around the streets of Brixton Hill and Streatham Hill can see that many flats are now occupied with people with City jobs who look to Clapham and Balham as much as to Brixton.