The Central American migration caravan currently making its way towards the United States is further exposing the cultural Grand Canyon in American politics. Like the 2015 Migrant Crisis in Europe, it is a vivid example of how global demographic shifts are fracturing the West. A structural feature of our century, these population dynamics will continue to divide western societies for decades to come.

This new schism springs from several forces. First, the unprecedented post-1960s level of long-distance migration from the developing world to an aging West. Second, the Left-wing ideological shift from class populism to pro-minority cosmopolitanism. The latter has successfully made any meaningful discussion of immigration and national identity taboo, with mainstream parties until recently steering clear of such topics for fear of being branded ‘racist’.

When liquor isn’t supplied by the market, bootleggers move in. So, too, the expanding anti-racist ideology hemmed in the major parties on immigration, opening space for populist Right entrepreneurs such as the Sweden Democrats or Donald Trump. In Britain, where the debate was more open, it was the failure of first Labour, then the Tories, to control numbers that permitted the BNP and Ukip to flourish.

Can anything arrest the polarisation of the West? By Paul Embery

Western countries’ ethnic majority share ranges from around 62% in America to over 80% in much of western Europe. However, this is steadily declining: the US non-Hispanic white portion will dip below 50% in 2050. Britain and other western European societies will follow suit around 2100. Cities will be transformed first: London is now minority White British and most major metropolitan areas in the US and Canada are majority non-white.

When conservative voters’ minds focus on this demographic shift, they are more likely to support Right-wing populism. US experiments which asked a set of white Americans to read about white decline found that it led them to lean towards the Republicans. I also find, using 2016 survey data during the primaries, that immigration rises up Americans’ list of priorities when reminded about this. In Britain, the share preferring lower immigration with lower average skill over higher numbers with higher skills jumps 25 points when people are asked to consider the long-term impact of sustained higher levels on the ethnic composition of Britain in 2060.

Actual increases in immigration have an effect similar to these experiments. As coverage of the increase grows, the public becomes more focused on the potential long-term loss of what I term the nation’s ‘ethno-tradition’, i.e. its characteristic ethnic composition of having a substantial ethnic majority alongside minorities. It also makes white majorities more aware that their group, with its collective memories, sense of common ancestry and cultural practices, is declining numerically in relation to other groups. Thus in the Bavarian elections where the AfD broke through, fully 100% of its voters agreed with the statement: “I worry that our culture is gradually getting lost”, compared with just 20% of Green voters.

Can anything arrest the polarisation of the West? By Sunder Katwala

Migration expert James Dennison and colleagues have shown that populist Right support rose alongside immigration in nine of 10 West European countries between 2006 and 2016. And while the Migrant Crisis was a shot in the arm for many of these populist Right parties, the 2008 economic crisis had no discernible effect, revealing the limited impact of economic hardship on populist Right voting.

Not all people react the same way to diversity and change. As psychologist Karen Stenner has shown, some prefer stability over diversity – an orientation which is between a third and a half hereditary. Attempting to compel such people into appreciating diversity can backfire, making them even more resistant. When Republican partisans are shown passages in which Trump is criticised as racist, many become significantly more pro-Trump.

Others, of course, welcome change and diversity. These people are more likely to live in cities like London and be highly educated. Yet, nearly 40% of London voted Leave and most Leave districts outside London have at least 40% Remain support. In fact, around a quarter of two-person households were divided over Brexit. Psychological disposition, not class or location, is key to explaining today’s emerging culture war.

And just as rising immigration galvanises some people, the rise of populism galvanises others – those cosmopolitan voters that David Goodhart calls the ‘Anywheres’, who are bound together by a moral worldview, rather than ethnicity. In the elections in Bavaria and Hesse, for example, the Green party enjoyed a boost as cosmopolitan voters deserted the Social Democrats, who represent a more traditional conception of the Left based around economic issues.

Can anything arrest the polarisation of the West? By Ben Cobley

This can take on a quasi-religious quality – what African-American writer John McWhorter terms the “religion of anti-racism”, something especially visible on elite American university campuses. The outbreaks of political correctness since 2013 speak to a reaffirmation of what I would call Left-modernism, an ideology fusing cultural egalitarianism with anti-traditionalism that emerged in the 1920s but only achieved wide penetration from the 1960s.

This polarisation occurs three times over. First, people respond differently to ethnic change, with conservative voters resisting it while liberals welcome it. Second, individuals divide by values, with cosmopolitan voters viewing opposition to immigration as racist, while conservatives reject this characterisation as politically correct. In a 2016 survey I conducted, I found 80% of Remain voters who are content with current immigration levels say it is racist for a White British person to want less immigration to maintain their group’s share of the population. Among Leavers without a degree, the share is precisely zero. In the US, the gaps are even wider.

Third comes electoral arithmetic: cosmopolitan voters celebrate the fact minorities tend to vote for Left-liberal parties like Labour. They look forward to the day when a rainbow coalition of white liberals and minorities brings forth a millennium of equality and diversity. Conservatives are insecure about this prospect and dig in.

Can anything arrest the polarisation of the West? By John Gray

As society grows more diverse, these divisions will steadily widen. This self-reinforcing triple-lock will tighten its grip. The US is at a more advanced stage in the process, but as the German regional elections show, Europe is following suit: the centre is hollowing out.

The remedy lies in what I term Whiteshift, the voluntary assimilation of minorities into the majority though intermarriage – a process which will need active telegraphing as mixing won’t be strong enough on its own to make much difference to social cohesion until the end of the century.

The Left needs to back away from excessive accusations of racism and dreams of radical social transformation. Conservatives should worry less about Muslims, Hispanics or the behaviour of other minority groups and focus instead on defending the interests of those who seek slower cultural change. This is not just about immigration levels, but should involve ethnic majority citizens inducting mixed-race children into myths of British ancestry.

If ethnic majorities come to see a secure future for their group in the rising mixed-race population, they may regain a sense of cultural security, allowing the West to overcome the growing forces of polarisation.