A very interesting article that I partly sympathize with. But if you are voting in the UK then how you vote has to be decided in the context of the choice of candidates standing in your constituency. It would be very rare that the Conservative Party candidate was the most liberal/progressive option. So actively supporting "centrist" Tories would be a self-destructive option for any self-respecting liberal-minded citizen.
We will all suffer if Cameron's brand of Conservatism fails
A Tory government is all but inevitable. The left is best served by engaging with the policies of a leader still open to ideas Jenni Russell The Guardian, Tuesday 3 March 2009
For 30 years anyone who thought themselves vaguely on the left has been able to rail against the nastiness of Conservatism. We deplored their devotion to the interests of the rich, their worship of the market, their callous indifference towards all those who couldn't flourish in their cruel, competitive world. We detested their xenophobia, racism, sexism and snobbery. We knew, from grim experience, how willing they were to let schools and hospitals crumble and public spaces become sad and fearful. We exhorted them to abandon their disgraceful politics - while remaining comfortably certain that they never would.
Well, now they're trying. There is a real battle going on within the Tories over the party's identity. A small group of determined people at the top is trying to pull the party behind some version of green, progressive, or compassionate conservatism. Its members are doggedly establishing the Conservatives in the centre, and sometimes the centre-left, of the political battleground. And yet, far from welcoming the fact that our political futures could lie in this more civilised territory, much of the left and its commentators are furiously trying to undermine or ridicule this move.
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http://www.guardian.co.uk/commentisfree/2009/mar/03/conservatives-david-cameron-politics