reposting because i like the point:
if Thatcher had been a left wing politician we'd judge her as an unconditional failure: her vision was of a dynamic industrial British capitalism, the result was the destruction of British industry and its replacement by finance capital and an economy doing worse than it had been relative to other European countries (it fell behind Italy for Christ Sakes! ITALY!) in the 1970s. Her aim was a more socially conservative Britain, but all she did was let people sublimate their economic resentment of her into support for social liberalization.
But we know she was a successful right wing politician, because a complete failure to implement your goals doesn't matter that much on the right - what matters is that the left (even the centre left) don't implement theirs.