The simple model of parties just described is often presented as if there are enduring broad and fundamental differences in society for the parties to represent. Yet it also assumes that somehow parties recognize and incorporate changes in society into party concerns. Parties do both of these. Some concerns have existed and endured over time, but remarkable social changes have occurred, pushing new concerns to the surface. Parties have responded, represented new issues, new constituents and areas, and changed their electoral bases, while also representing enduring interests.