Social democrats are inspired by social justice and equity. But they are also democrats, so they rely on the voters to determine those goals. The vogue assumption is that most voters are rational and rationality in the associated sense is that they know how to vote in self-interest. Since more people are poor, working-class, or working middle-class, theoretically, if these people unite to vote in common self-interest, wealth should wind up distributed, in the form of taxes and government benefits, to the majority of the population.
