What is missing in this analysis is that the ideological "incoherence" of the two parties 50+ years ago reflected a consensus in both parties about the general role of state. Both Republicans and Democrats tended (although not uniformly) to have accepted the New Deal, but both also tended to accept generally held American values (social, political and economic). Today, the Democrats in particular are at odds with key aspects our nation's basic principles and certainly since the late 1960's have been actively working to change them. The resulting division/partisanship is much like that of the pre-Civil War era. Ultimately, the division will be resolved and a new consensus will take its place, just as it did then.