A recent New Yorker cartoon: A TV anchorman with two figures standing behind him, each in front of a wall map: “That was Brad with the Democratic weather. Now here’s Tammy with the Republican weather.”

At Trump Rally (source)
It seems that political disputes have gotten almost that bad (and, of course, we are reminded of the arguments over climate change). I recently claimed that the key reason that Donald Trump, a woefully unfit candidate, received 46 percent of the popular vote (while in 1964 Barry Goldwater, an ideological outlier but a personally respected senator, received only 38.5% of the vote) is the polarization of recent decades. About nine of ten Republicans ended up voting for their party, whatever they felt about its standard-bearer.
Recent studies on polarization underline the surging emotional hostility between party partisans, those who care about politics. (Let us remember the 40 to 45 percent of eligible Americans who do not care enough to vote even in presidential elections are not engaged in this divisiveness.) And while it would seem that Republicans and Democrats live in alternative worlds with “alternative facts,” if not alternative weather, increasingly their differences are less about reality than about identity and the values and the emotions tied to those identities.
Who Am I?
Many studies have documented the widening gap between partisans of the two parties. The blatant contempt that Republicans and Democrats express towards each other in surveys has escalated in the last 20 years (pdf). A 2015 study found that party prejudice is stronger than racial prejudice. Republican and Democratic partisans have become increasingly different in their positions on issues, on moral concerns, and even in styes of life which seemingly having nothing to do with politics (e.g., here). In their paper titled “Why do Liberals Drink Lattes?,” Daniel DellaPosta, Yongren Shi, and Michael Macy document the ways in which liberals and conservatives differ culturally (although they actually have no data about coffee). That one side likes to bird-watch in Patagonia jackets and other to bird-hunt in camo has no logical connection to positions on, say, the estate tax or who should be president, only but crucially a psychological connection.
Some scholars believe that there must be deep thematic connections between voting and tastes in, for example, music. DellaPosta and colleagues argue, in contrast, that once some distinction appears, even if by accident, between what “we” do and what “they” do, then people begin to sort themselves in accordance, adopting the cultural tastes of their fellow partisans and generating separate lifestyle enclaves–wine and Prius communities versus beer and pickup communities. Importantly, for politically engaged Americans, the tent poles of their communities are their party identities. (DellaPosta reports in an email that the connections to party identification strengthened modestly over time.)
People are heavily invested in their identities, their answers to Who am I?, Who is like me?, and What do we value? Challenges to someone’s identities–you are not the honest, or Christian, or giving, or tolerant person you think you are–provoke strong defensive reactions. In a recent special issue of the Public Opinion Quarterly devoted to the polarization topic, Lilliana Mason reports finding that those who seem especially rooted in identities such as evangelical Christian, secular, or black, were most likely to respond either with anger or with enthusiasm to political messages that threatened or promoted their party affiliations. That is, she argues, challenging people’s identities rather than challenging them on issues is what really generates political emotion.
Speaking of issues, a pair of studies in the Quarterly Journal of Political Science (here and here) make the case that seeming conflicts between Democratic and Republican survey respondents on facts–say, on the unemployment rate, or on crime trends–are best understood not as expressions of different realities, but rather as expressions of identities. Many partisans take factual questions posed by pollsters as opportunities to declare who they are and whose side they are on. For instance, partisan respondents describe the economy as booming when their party holds the White House and as miserable when their party doesn’t. However, if pollsters offer respondents money for a correct answer (or to admit that they do not know the answer), the big gaps between Democrats’ and Republicans’ replies narrow greatly. Identity and emotion lie behind the answers at least as much as understandings of the facts–and perhaps more so now than for decades.
In the Current Emergency
The new incumbent in the White House, knowingly or not, played to this partisanship quite well. Issues and facts and consistency were secondary, but identity–white, native-born, Christian, nationalist–and hot anger were primary to his appeal. Emotions still run high. Partisanship is probably increasing as I write.
Through this, much of the American public has sat on the sidelines. They didn’t vote; they don’t follow the news. Trump seemed to have brought just enough of them onto the field of political battle. Who, if anyone, will bring others onto the field in years to come?
………………
Update (Feb. 28, 2017):
More on lifestyle differences and politics here.