Left-wing ideas are formed behind a wall of protection, in a 'temperature-controlled' environment like hothouse flowers. They can't stand rigorous testing. As more and more of society is subjected to rigorous debate via the emergent conservative media, leftism will disappear.
Left-wing politics is dead. The real (coming) battle is between conservatives and libertarians over moral issues.
Within the context of reasoned debate this has been correct for a long time, however what I think of as liberal politics is not so much dead, as it is marching on as a kind of undead facism.