Liberalism and atheism
Alan Roebuck wrote in the Intellectual Conservative the following:
Western Civilization is under the effective control of the worldview of the Left, commonly called "liberalism." I describe liberalism as our "unofficial state religion." And the philosophical basis of liberalism is atheism: either explicit atheism, or the de facto variety that only denies that anything can be known about God. It is this freedom from God and His authority that makes liberalism the radically destructive force that it is. 
In respect to the theory of evolution and liberalism, in the United States, CBS News reported in October 2005 that the Americans most likely to believe only in the theory of evolution are liberals. Since World War II a majority of the most prominent and vocal defenders of the theory of evolution which employs methodological naturalism have been atheists.
While atheists play a prominent role in regards to liberalism, there is also those who subscribe to liberal theology.