At the end of the day, who votes for the individual in a national election? You vote for the party. Look at my last UK constituency, Witney, yes I know, I call him Dave in the pub. When Douglas Hurd retired, Shaun Woodward took over. When he defected even if he was a good guy (doubt it) do you honestly think that the Chipping Norton set would vote Labour. They would prefer to run themselves over with their Range Rovers or hang from the beam of their 17C farmhouse by their Armani scarf.