Every ten years, 'on the fours' Pew Research looks at polarization in the U.S. The 2014 report was shocking and the lack of sufficient dissemination has led to the misdiagnosis of the underlying reasons for Sanders, Trump and Cruz.
At the core of the report are a set of ten questions to which respondents are asked to choose one of two answers, one 'conservative' and one 'liberal.' They then subtract the number of liberal answers from the number of conservative answers. A 10-0 or 9-1 split way is deemed to be consistently conservative or liberal. 8-2 and 7-3 splits are deemed to be mostly conservative or liberal and 6-4 and 5-5 are deemed to be mixed.
Between 1994 and 2004 the percent that were consistently ideological remained constant at 10% and 11%. However, in 2014 it had doubled to 21%. This was not partisan with conservatives increasing 6% and liberals increasing 4%. The perccent that was mixed did not increase from 1994 to 2004. However, from 2004 to 2014 it fell from 49% to 39%.
Sanders, on the other hand, is the result of many Democrats' desire to no longer settle for 'Liberal Light'. They do not think that compromise is the correct approach. They believe, and I have spoen many supporters, that if people are just properly educated on what Sanders beieves that he will sweep to nomination and probably the White House. They truly don't understand that a huge portion of American voters, if they better understood what Sanders wants for the U.S. would be horrified.
I start a basic syllogism
It is wrong to compromise one's principles
Politics is the art of compromise
Therefore, politics is wrong between groups with different principles
This is why we are headed for a divorce and why we have the emergence of uncompromising candidates such as Sanders and Cruz. Fifty years ago, gay marriage would be out if the question. Abortion was illegal and few people had a serious problem with that.
In other words, most of the points of difference between Republicans and Democrats that are principled in nature are new. We no longer have a single culture with shared values and where the Republican and Democratic parties once had political differences they now have cultural differences.
The divorce may begin with the secession of Texas and cascade from there. But that is a different post.