In my previous post, I noted that almost all the counties President Barack Obama won have become more Democratic since 1992, while almost all the counties Senator John McCain won have become more Republican since 1992.
In fact, comparing maps of the 2008 presidential election and the county changes from 1992 indicates a striking correlation.
Here is the 2008 presidential election:
Here are the changes from the 1992 presidential election:
On the one hand, all this is somewhat intuitive. If a Democratic candidate does well in a specific place, he or she probably improved on a previous Democrat’s performance there – and vice versa. Moreover, these maps do not imply that all blue regions became more Democratic (nor the opposite); rural Appalachia, in the most famous instance, has trended sharply Republican, while much of suburban American has gone in the opposite direction.
On the other hand, this phenomenon does not constitute a mathematical rule. If a Democratic candidate wins a county, that doesn’t necessarily imply that he or she improved upon a previous Democrat’s performance. He or she could have done worse but still won; the previous Democrat might have overperformed, or the Republican might have encouraged cross-over voting.
Yet by and large, this has not been the case. Obama practically always outperformed former President Bill Clinton in today’s Democratic counties. Mr. McCain practically always overperformed former President George H. W. Bush in today’s Republican counties.
Taking a look at selected states provides a powerful illustration of this fact.
Here is California:
Here is Colorado:
All this implies something rather disturbing: electoral polarization has been steadily increasing. Obama only improved on Mr. Clinton’s performance in the counties Obama won. McCain only improved on Mr. Bush’s performance in the counties McCain won. The almost total lack of cross-over gain suggests that each party has come to depend on deepening their base, rather than widening the electorate and appealing to moderates.
That America is getting more divided has, of course, been known for a fairly long time. In some ways the maps exaggerate the polarization: 1992 Clinton appealed to many Republicans, while Obama’s strength lay amongst the Democratic base. Then there is the Ross Perot effect, which lowered margins in both party strongholds (e.g. New England, the Plains states).
But perhaps a bit of exaggeration is needed. Polarization has rarely been good for any country, and its increasing prevalence bodes poorly for the future of the United States. A map like this provides a potent illustration of polarization in action; indeed, I have never encountered a more striking image of its increase. Such a picture might do us some good.