The L word
Altercation has an analysis of the demise of liberalism that is as concise and as cogent as anything I've seen on the subject:
Although liberals accomplished great things during the first three quarters of the 20th century, thereafter they stumbled badly. When they encountered resistance to black civil rights among poor and working class whites—some of it racially motivated some of it not—rather than dealing with the resistance politically, liberal elites sought to impose solutions from above by taking advantage of their privileged access to judicial and executive power. Then, rather than telling Americans honestly about the likely costs and consequences of a military intervention in Southeast Asia and trust them to make the correct decisions, they used lies and deception to trick voters into supporting an unwinnable war that was fought mostly by the poor and working classes; and when the war came too close to home, they quickly forgot about the lower class combatants and their sacrifices they had made. Then after liberals’ attempt to support guns and butter set off hyperinflation to erode the real value of wages, they callously thought up new ways to spend the windfall of tax revenue rather than adjust tax brackets to relieve the unsustainable burden on the middle class. Finally, when faced with political revolt because of these misguided policies, they retreated into arcane ideologies to wage a rearguard cultural insurgency from the safety of the ivory tower. Is it any wonder that liberals lost the public trust?
Vincent Cannato comes to much the same conclusion in his compelling book "The Ungovernable City: John Lindsay and the Struggle to Save New York." I highly recommend it.