This post is part of Polyarchy , an independent blog produced by the political reform program at New America , a Washington think tank devoted to developing new ideas and new voices.

In 2016, race and identity has emerged as the central dividing line in American politics. Though race has always lived close to the surface of politics in the US, it has rarely been so explicitly front and center in political campaigns. So how did this happen?

The easy answer is Donald J. Trump. True, Trump was the first modern Republican to win the nomination based on racial prejudice. And, yes, racial resentment does more to explain support for Trump than even ideology.

But Trump is not acting in a vacuum. He is instead riding forces set in motion a half-century ago. His identity-based nomination should be seen as the logical culmination of Republicans' 50-year "Southern strategy" to make politics primarily about race and identity instead of economics.

This history is not just an academic exercise. It's crucial for understanding where politics is headed. Treating Trump's nomination as a historical aberration allows one to think that there is some returning to "normal." Viewing Trump's nomination as a historical culmination suggests instead that there is no going back, and that "normal" is just a name we call a bygone era.

For Republicans, the irony is that this strategy reached its full completion at precisely the moment when it was no longer a winning national strategy. For Democrats, with their coalition increasingly split along class lines, this is looking more and more like the one issue that can keep the party coalition together. No wonder, then, that this is the issue on which Hillary Clinton is now hitting Trump hardest.

But while the Democrats do appear to be benefiting in this election at the presidential level, it's not yet clear that this is truly a long-term winning issue for Democrats. Much of it depends on how Republicans shift in response to 2016, and whether Democrats overreach. But to understand what might come next, we first need to understand better how we got here.

Politics is a battle over the dividing line of conflict

In order to make clearer sense of the political history of how we got to now, a basic theoretical framework will go a long way.

The theoretical framework comes from political scientist E.E. Schattschneider's 1960 classic The Semi-Sovereign People: A Realist's View of Democracy in America. "What happens in politics," Schattschneider writes, "depends on the way in which people are divided into factions, parties, groups, classes, etc. The outcome of the game of politics depends on which of a multitude of possible conflicts gains the dominant position."

Politics involves many issues, across multiple dimensions. But in a two-party system like the one we have in America, there can really only be one primary dividing conflict at any given time, since there are only two parties. You can think of it as two teams forming around some basic divide, and then subverting whatever other internal disagreements they have for the sake of team loyalty. Yankees fans and Red Sox fans, for example, may disagree internally over many things. But in a political system organized around the Yankees versus the Red Sox, they would be in different parties and put other disagreements aside.

Schattschneider's fundamental insight was that the fight over this primary dividing line is the most important fight in all of politics. That's because this is the fight that determines which party is in the majority and which party is in the minority, and which issues get argued about between the parties and which issues get argued about within the parties.

However, because public opinion does not exist on a single dimension, any alignment contains within it many disagreements, which tend to grow over time. For example, Red Sox fans may be united over their hatred of the Yankees. But a coalition organized around baseball loyalties probably cuts across class. So both fan-based parties might disagree internally over tax policy. In the offseason, when they don't have baseball to focus on, an internal civil war over tax policy could split both parties.

Throughout most of American history, there have been essentially two main divisions in American politics: over economic policy (essentially: more or less government intervention in the economy) and over social/cultural/identity issues. In The Two Majorities, a sweeping study of American public opinion, Byron Shafer and William Claggett summarize the first, economic dimension as "tapping arguments over the appropriate (re)distribution of economic benefits to the less fortunate," and the second, social/cultural dimension issues as about "the implementation of American values — values that define appropriate social behavior."

In mass opinion surveys, beliefs on these two issues tend to be at best weakly correlated. Or, put another way, most voters are not ideologues. Knowing most people's views on government regulation of business will tell you very little about, say, their views on abortion. (Except for maybe the 10 to 15 percent of respondents who pay very close attention to politics, including those most likely to be reading this article).

It follows that a politics organized around abortion could look very different from a politics organized around business regulation. To illustrate, consider a very simple political system with just these two issues, and two parties organized around these two issues as follows:

The Freedom Party: a pro-choice, anti-regulation party

The Populist Party: a pro-life, pro-regulation party

Imagine also that 60 percent of voters are pro-choice and 60 percent are pro-regulation. In such an environment, the Freedom Party wants voters to make abortion the No. 1 voting issue, because most voters agree with the Freedom Party that women should have the right to choose. The Populist Party wants voters make business regulation their top voting issue, since most voters agree with the populist party that businesses should be regulated more. The party that makes the election about their issue is the party that wins the majority.

This is a very different way of thinking about politics than the one-dimensional "median voter theory," which assumes that parties will converge on a mythical "center."

The median voter theorem, however, has two main conceptual flaws. First, it assumes that political ideology is one-dimensional, which would create a meaningful middle on which to converge. But again, public opinion is two-dimensional (at least).

Second, and perhaps more problematic, is that the median voter theorem assumes political leaders can just move around this one-dimensional issue space at will to respond to voters. In reality, they are constrained by activists and donors who often have non-majoritarian positions but provide the necessary resources by which parties and candidates operate.

In the simple political system I've sketched out, the median voter theorem would predict that both parties would become pro-choice and pro-regulation, since that's what the majority of voters want. And maybe they should.

But to make this example realistic, we should probably say the Freedom Party gets its main funding from cosmopolitan business leaders, who would pull funding immediately if the party shifted to a pro-regulation position. By contrast, the Populist Party relies on armies of pro-life grassroots volunteers and donors, and would fall apart without this support.

Both of these parties are then stuck with certain positions — their joint challenge is to use their resources to make politics about the issue on which they have the majority, while obscuring the issue on which they are in the minority.

Though this is a simplified example, it comes far closer to how political parties actually operate than the median voter theorem. It offers the same reason why neither Democrats nor Republicans have converged on the middle in decades: because they have activist groups with non-majoritarian policy goals.

Parties generally win when they can divide politics in a way that makes the public happy because that party is on the more popular side of the central voting issue, but also makes the activist groups happy because the parties have managed to get the activist groups' demands into the party's agenda without making it the central voting issue. Parties generally lose when they are forced to choose between public opinion and their activist groups because the central dividing line of politics forces them to do one or the other. (This point about the importance of activists I get from Gary Miller and Norman Schofield's thinking on realignment.)

To summarize briefly, politics is about shifting the line of conflict. Coalitions and majorities are both made and unmade depending on the line of conflict. Losers are always trying to shift the line of conflict; winners are always trying to maintain the line of conflict.

How civil rights realigned American politics — slowly

With this basic bit of theory in place, we are now better poised to tackle the history of how we got to 2016.

Our story effectively begins in 1932, when Democrats formed a majority coalition that included Northern liberals and Southern conservatives. The Great Depression had made economics the fundamental dividing line of conflict. And with Republican President Herbert Hoover getting the blame for the collapse, Democrats were on the winning side of the issue.

Now, if the median voter theorem explained the world, Republicans would have simply become the party of the New Deal as well — as some would say Eisenhower attempted to do. But Eisenhower's New Deal–light Republicanism angered the activists and economic elites in the Republican Party, who still wanted to undo the New Deal and who were sure that if they really truly opposed the New Deal, public opinion would miraculously move to their side.

When the far-right economic conservative Goldwater lost in 1964, however, it became clear Republicans couldn't win purely on limited government as a defense of liberty. They would have to attach limited government to a winning position on some other issue that would split the Democratic Party...

Like all majorities, the Democratic majority from 1932 to 1964 contained within it the seeds of its own destruction — in particular, an internal conflict between Northern liberals and Southern conservatives over the issue of civil rights. Eventually, Northern liberals became the majority faction within the Democratic Party and exerted pressure, and Democrats passed a series of civil rights bills into law.

And with that, the Democrats effectively lost their winning political hand for the sake of moral principle. The civil rights laws created a backlash among Southern white Democratic conservatives and Northern working-class whites who were most directly affected by urban riots, and housing and school desegregation.

This gave Republicans the cross-cutting issue with a clear majority they needed: race and identity. With Nixon's strategic guidance, Republicans went full steam ahead in making it the central dividing line in American politics.

They were certainly aided in this effort by Democrats, who struggled to speak to the urban unrest that drove many former Democrats to the Republican Party, or to acknowledge some of their own hubris in the power of a government run by Ivy League intellectuals to solve deep social problems. Democrats also nominated George McGovern to be their standard-bearer in 1972, whose label as the effete candidate of "acid, amnesty, and abortion" stuck, and also stuck with Democrats.

Moreover, as the economy stagnated in the 1970s, and businesses choked on a slew of new regulations and inflation increased, Democrats' traditional advantages on economic issues also waned.

With Ronald Reagan's election in 1980, Republicans solidified a winning coalition that successfully strengthened the appeal of "limited government" beyond economic conservatism, where it had traditionally lived. "Limited government" now also meant not meddling in the private lives of citizens to enforce some elitist Ivy League intellectual's idea of racial justice, and not asking middle-class taxpayers to pay welfare support for poor black people.

The great synthesis was the seemingly counterintuitive idea that everything government tried to do, from regulate business to provide free school lunches, was somehow interfering with the free market. From there, the link to anti-communism was obvious, with communism being the opposite of capitalism. And since communism was also opposed to religion and therefore the enemy of Christianity, Republicans were the natural home of traditional Christians, too — especially as compared to the socially liberal, abortion-loving Democrats.

But like all winning political coalitions, this, too was full of internal contradictions. In particular, many of the economic conservatives (who tended to be more libertarian and thus more culturally cosmopolitan) and many of the cultural conservatives (who tended to be former New Deal Democrats and thus very supportive of universal entitlements like Social Security) didn't have a ton in common, other than feeling like they didn't have a home in the Democratic Party (though for different reasons).

You can see this basic story nicely in a helpful graphic produced by political scientist Jennifer Victor, who used it in a recent piece explaining Miller and Schofield's realignment theory.

This graph nicely shows how the dividing line in American politics has shifted in clockwise fashion, producing different political alignments and different majorities.

How Republicans and Democrats swapped voters

Beneath these shifting positions at the top was a significant cross-party swapping of voters. Republicans and Democrats essentially underwent a four-decade exchange program. Democrats sent Republicans their non-college-educated, culturally conservative white voters, mostly in declining rural and exurban areas, who had once been the core of the New Deal. In return, Democrats got culturally liberal wealthy professionals, largely in prosperous urban and suburban areas, many of whom were once "Rockefeller Republicans" and had once opposed many elements of the New Deal.

This happened slowly, because partisan loyalties are really sticky and most voters don't play close attention to issues. (To really understand how sticky partisan identities are, consider that up until 2010, Democrats were a majority in the Alabama state legislature).

It also happened slowly because in the 1990s, Democrats managed to stem some of the flow by taking more conservative stands on race and culture under the leadership of Bill Clinton, who won a bunch of Southern states. But it could only be a temporary hold, especially once Republicans started winning back southern congressional seats and retook the House in 1995.

As one way of observing the shifting voter bases of the two parties, consider the below chart, which looks at the state-level correlation between voting Republican for president and the share of state population with a college degree. In 1992, there was no correlation. In 2012, there was a notable correlation: Republicans did far better in less-educated states; Democrats did far better in highly educated states.

For Republicans, this initially looked like a really good deal, more like a two-for-one swap. And it largely was, from the early 1970s until about the mid-2000s.

But the deal had a long-term liability. America was steadily becoming more diverse, and more highly educated. And the younger generation was much more culturally and socially liberal than the previous generation. Republicans might have been converting more Democrats to Republicans than vice versa. But Democrats were making greater gains among new voters, and also doing better and better among increasingly cosmopolitan wealthy Americans. What looked like a losing coalition for Democrats in 1972 would be a winning coalition for Democrats nationally in 2008.

There was also second problem for the Republican elites whose vision of "limited government" was always far more motivated by economic conservatism than by cultural conservatism. By the mid-2000s, they were becoming more and more of a minority within their party as the party had become more dependent on conservative working-class whites to win elections.

And while these voters could be convinced to support "limited government" and "free enterprise" as abstract moral principles, they also had no great love for Wall Street, or for corporate CEOs or globalization. More often than not, they were from rural and exurban places that had increasingly become hotbeds of political resentment, places that had been on a steady multi-decade economic decline as more and more talent and capital investment flowed to the largest cities, mostly on the coasts. Their communities were slowly dying, both literally and figuratively.

These voters had no interest in Republican elites' priorities of voucherizing Medicare or privatizing Social Security. They wanted their entitlements. They wanted government to do more for old people and the middle class. And they were really concerned about immigration. And as Republican elites failed to respond to their concerns, these voters grew more and more frustrated.

Republican elites face a dilemma

Given this dilemma, Republican leadership had essentially two choices. One was to recognize that the Republican Party was becoming the middle-class party, and to offer a set of economic policies targeted to help these increasingly struggling middle-class voters — perhaps something akin to the "Sam's Club Republicanism" that Ross Douthat and Reihan Salam argued for in their 2008 book, Grand New Party: How Republicans Can Win the Working Class and Save the American Dream.

The other choice was to instead continue to push the very economically conservative policies most preferred by the now minority-within-the-party wealthy establishment Republicans by turning "limited government" into a nearly religious crusade, and feeding the overarching argument that the federal budget was nothing but a giant transfer program from strained "maker" middle-class taxpayers (mostly white) to poor "taker" criminal welfare recipients and illegal immigrants (almost entirely black and Hispanic). And, even more apocalyptically, that any expansion of government was akin to socialism and communism and fascism all rolled into one horrible totalitarian nightmare overrun with illegal immigrants, which just happened to be Barack Obama's secret black Muslim takeover plan for America.

Whether or not Republican leaders actually believed any of this rhetoric is hard to say. But these are the kinds of things Republican voters began to say in the 2010s. And Republican leaders did nothing to stop it. After all, all this rhetoric allowed the party to keep its donor-class activists happy by obscuring these donors' deeply unpopular policy goals under the guise of something else.

The post-2008 divergence

Take a look at the graphs below, which measure how Republicans and Democrats have felt toward black and Hispanic people over the past several decades. (The measure I use is a standard political science metric, the "feeling thermometer," which asks respondents to rate their feeling toward individuals and groups on a scale of 0 to 100).

For as far back as we have good measures, Democrats have felt slightly warmer than Republicans toward black and Hispanic people. As we would expect.

But clearly something happened around 2008 to trigger a divergence. If the previous four decades had been about moving the non-college-educated whites most prone to racial prejudice from the Democratic Party into the Republican Party, that transformation had now mostly been completed. And now that it was completed, the parties were set for a major divergence. The elements within each party that might have held it back were now squarely in the minority.

Events also appear to have contributed. In particular, a black man named Barack Hussein Obama became president of the United States, and rapid increases in immigration created a sense of crisis in many places. Both of these appear to have provoked measurable backlashes.

How Obama's election fueled a backlash

When it happened in 2008, Obama's election was widely viewed as a landmark of race relations progress. But looking back, it now seems increasingly clear that his presidency activated a racist backlash among a particular segment of the population.

Political scientist Michael Tesler, for example, has found that "[o]ld-fashioned racism returned to white Americans' party identification in the early Obama era because the country elected an African-American president from the Democratic Party." He also found that whites with strong racist attitudes turned much more sharply Republican following Obama's election, including some who had previously been Democrats.

More recently, in a new book, Post-Racial or Most-Racial: Race and Politics in the Obama Era, Tesler documents what he calls "the spillover of racialization." That is, because of "Barack Obama's omnipresent position as a historic racial figure, and his embodiment of race as the first African-American president," racial attitudes were constantly being activated.

As a result, racial attitudes started to independently predict feelings towards seemingly unrelated issues, like health care. And issues that might not have once been partisan issues, like whether 12 Years a Slave deserved an Oscar for Best Picture, have became deeply partisan.

It's also worth noting that once Democrats were freed of their remaining "blue dog" Southern conservatives in Congress after the 2010 midterm landslide, and they felt increasingly confident they could win national elections with the "Obama coalition" of racial minorities and white liberals (essentially following the strategy Thomas Schaller outlined in his 2006 book Whistling Past Dixie), they had fewer reasons to moderate on racial and social issues, as Bill Clinton had needed to in order to win nationally in 1992 and 1996.

It's no surprise, then, that Democrats have recently taken strong stands on same-sex marriage, have felt more comfortable speaking to the concerns of the Black Lives Matter movement, and have even been willing to take more aggressive stands on gun control. And given all this, it's no wonder that socially conservative whites have become so convinced their country is being taken from them.

How immigration fueled a backlash

Immigration has also contributed. It's important to understand that between 1990 and 2014, the share of foreign-born citizens in the United States went from 7.9 percent to 13.9 percent — a near doubling. The last time the share of foreign-born citizens got this high (about 100 years ago), it provoked enough nativist backlash in the 1920s to largely close the borders for four decades, until 1965.

It appears that the rising tide of immigration has indeed provoked some backlash, and that backlash has been channeled into the Republican Party. Political scientists Marisa Abrajano and Zoltan L. Hajnal have found that negative views about immigrants contribute to stronger identification with the Republican Party among whites, even controlling for all the usual variables that typically explain partisanship (including ideology). They also found that whites with strong anti-immigration views actually shifted their partisan identification from Democrat to Republican in the late 2000s. These findings are reported in their 2015 book, White Backlash: Immigration, Race, and American Politics.

Some of this, Abrajano and Hajnal argue, is because Republican politicians "have been much more vocal and adamant in their opposition to immigration." Therefore, "the millions of white Americans who feel real anxiety about immigration are drawn to the political party that has promised to ease such concerns." Meanwhile, "The pro-Democratic tendencies of the growing Latino population have dramatically altered the racial group imagery of the Democratic Party."

One likely reason Republicans have turned much more anti-immigrant is probably because red states have generally seen a much greater percentage increase in immigration than blue states. Arkansas, for example, has experienced a 346 percent increase in the foreign-born share of its population. Admittedly, the 2014 population of Arkansas was only 4.7 percent foreign-born. But it was just 1 percent in 1990. By contrast, California experienced a mere 25 percent increase — and from a large existing population.

Consider the graph below, which places states on a grid based on the share of immigrants living in the state in 1990, and the percentage increase in immigration from 1990 to 2014.

The pattern is striking. Of the 20 states that experienced more than a doubling in the foreign-born population share between 1990 and 2014 from a low baseline (under 3 percent of the state population), Mitt Romney won 18 of them (90 percent), losing only in Minnesota and Iowa. Or, looked at another way, of the 24 states Romney won in 2012, 18 of them (75 percent) were states that had seen rapid increases in immigration (more than 100 percent) after a history of low immigration.

These percentage changes matter. In an exhaustive 2010 study, political scientist Dan Hopkins demonstrated why some places became much more anti-immigrant than others. "A sudden increase in the number of immigrants," he concluded, "is the most powerful predictor of which localities consider anti-immigrant ordinances." In a review essay on the immigration literature in political science, Hopkins and co-author Jens Hainmueller conclude, "Immigration is thus an issue with the potential to emerge suddenly and to destabilize existing political alignments"

Moreover, increases in the foreign-born share of the state population appear to help Republicans. The greater the increase the foreign-born share of the population between 1990 and 2014, the more Republicans improved their two-party vote share for president between 1992 and 2012. Notably, four of the five states with the highest percentage increases (Kentucky, Tennessee, Arkansas, and Georgia) were states Clinton won in 1992.

And then ... Trump

Now, in retrospect, it becomes increasingly clear how the Republican Party got to a place where it was primed for Trump's white grievance message. Republicans spent the past half-century winning over socially conservative, non-college-educated whites on issues of race and identity, to the point that these voters became the dominant faction within the party. With little else to hold the party together, Republican leaders doubled down on these issues over the past decade. They were also helped out by events.

To be sure, a good number Republicans strongly disagree with Trump's "textbook racism." And many have previously advocated for Republicans to broaden their electoral appeals beyond resentful whites.

And to be sure, not all of Trump's appeal is based on racism. He was also the only Republican candidate to speak directly to the economic uncertainties that many downscale Republican voters have been feeling, and the only Republican candidate to stand up, at least rhetorically, for Social Security and for taxing the wealthy (even if his campaign platforms have not always reflected these details).

But the reality is that Trump won the nomination with the most explicit racial language we've seen from a modern presidential candidate. His campaign resonated because it connected with a sizable piece of the Republican electorate.

The great irony for Republicans is that what began as a clearly winning strategy in the 1960s now looks like a clear loser at its culmination in the 2010s. The racialized politics of 2016 have probably handed Democrats a winning issue in a year in which the election fundamentals probably slightly favored a Republican.

Had Trump run a more conventional campaign focusing on the economy and making the standard out-party case for change, he might now be winning. Instead, he tried to make it a campaign about the character and identity of the nation. He is now losing that contest. And now that he has set the tone, the Democrats are unlikely to let him shake it off, even if he tries to. More and more, Hillary Clinton is trying to make this an election about Trump's racist comments and associations.

It is now Democrats who appear benefit from culture and identity being the central issue in American politics, at least in a national election like the one for president.

And as the Democrats are increasingly split internally by class, this may now be the one issue that holds the party together. In the future, then, it will likely be Democratic Party leaders who want to keep culture and identity as the central dimension of conflict in American politics.

Whether Democrats succeed depends in part on what Republicans collectively decide to do. But given the forces that have led to 2016, it seems unlikely Republican can reorient themselves anytime soon. Like Democrats, Republicans are also internally divided by class but held together by identity.

In other words, it seems we are likely to have a politics dominated by race and identity for the near-term future.

Still, there are many uncertainties over whether this will benefit Democrats or Republicans beyond 2016. I'll tackle some of these in a follow-up post tomorrow that looks much more at what is likely to happen in the next decade or so.

Note: The follow-up piece can be read here.

Special thanks to Chayenne Polimedio for her help researching this piece, and to Tyler Richardett for his help with the graphics.