This isn't another "Donkeys are from Venus..." kind of essay.
One sign is the changing mood of the two parties' constituencies, their primary electorates. Traditionally, Republicans have been regarded as docile, "easily led," as a political reporter once characterized evangelical Christians. Traditionally, Democrats have congratulated themselves for their critical, skeptical nature and refusal to take orders.
That's not how the two parties look today. Democrats look like girls in the second grade, who when they finish their workbook exercises fold their hands on their desks and wait for Teacher's next order. Republicans act like second-grade boys, wiggling in their chairs, jumping up and pulling classmates' hair, making flatulence jokes and dodging Teacher's reproof.
Republicans give scathingly negative ratings to their party leaders, while placid Democrats give unanimous favorable ratings to Barack Obama and Hillary Clinton. That's the main reason Obama's second-term job approval has remained unprecedentedly steady while George W. Bush's plunged after disorder in Baghdad and New Orleans.