I'll be talking more about liberal religion, but first a brief note about religion and politics. It seems to me that when any religious institution loses its spiritual focus, something has to move in to fill the void. In mainline denominations, political activism often replaces evangelism as the main focus. Now activism isn't wrong, in and of itself, but neglecting evangelism is. We are commanded to be witnesses, as well as to do good works.
So many of today's denominations have lost their spiritual focus, and hence their evangelistic drive, because there is nothing spiritual left to talk about anymore.