Although most Americans don't call themselves liberal, they like most liberal policies. When polled about policies without the label “liberal” attached, they support greater income equality, higher taxes for the rich, controlling the banks, and strong Social Security, Medicare, and education. They even support more foreign aid than we currently give (although they don’t know it), and they think it is time our wars should come to an end. Despite these policy preferences, many people buy into conservative rhetoric and liberal-bashing because that's all they ever hear - and that's all they ever hear because the center-left establishment doesn't display the fortitude to vocally stand up for its purported beliefs. In the end, all we really have to do is confidently argue for our principles, repeatedly and effectively, until they sink in. Democracy has the strength of numbers, when it has the stamina to remain united against propaganda and internal division.
Political fortitude in the public debate is critically important because it is ultimately necessary to making and keeping the world fit for human habitation, socially, politically, and environmentally. How our side conducts itself determines, in the long run, whether it wins or loses the ideological struggle. It determines the shape of the political conditions in which workaday political battles are fought, and determines whether tactical wins accumulate into strategic victory or whether we keep winning battles but lose the war. In the long run, the side with the most political fortitude wins. And the winning side gets to determine what policies are enshrined into law and put into practice, and that in turn determines who gets rich and who gets poor, who has power and has none, and even who gets to live and who has to die. I am not being hyperbolic: whether grandma continues to get her Social Security check, whether a sick father gets life-saving medical care, whether regular people prosper or struggle, whether bloody wars of choice are fought or not, even whether civilization survives climate change, all depend on how long and hard and courageously we are willing to fight, politically, for our principles. Political calculation can achieve none of it. Whether the Left develops strength and sterness or whether it continues to appease, capitulate, and cede ground is going to determine to a great degree the kind of world we and our children will live in.
The main barriers to achieving social justice are the Right's resistance and our own lack of political will. Political fortitude - political strength and stamina - will help to overcome both barriers. If the Left does not develop this virtue, then it will continue to lose, I guarantee it.