An Eton trifle

Can anyone with politico-linguistic nous explain to me how David Cameron is rationalizing his campaign slogan against the very definition of his party?

con·ser·va·tive (kn-sûrv-tv)

adj. Favouring traditional views and values; tending to oppose change.

Or is a "vote for change" actually a "vote for change back to the opposition of change"? Je ne comprende pas.