There are many similarities but some significant differences in the attitudinal and demographic profiles of supporters of Trump in the USA, on the one hand, and supporters of Brexit in the UK, on the other.
1. The most important similarity has to do with attitudes: both groups are distinguished by their negative opinions towards "multiculturalism" in general and towards immigration in particular. Indeed, according to a recent poll by the Pew Research Center, only 40% of Trump supporters believe that increasing the number of people from different races/ethnicities makes the US a better place to live (compared with 57% of all registered voters), while fully 79% favor their candidate's idea of building a wall along the entire border of Mexico (compared with 38% of all registered voters). Likewise, according to the Lord Ashcroft poll, fully 81% of Brexit supporters register a dislike of multiculturalism (compared with 39% of the general public), and 80% register a dislike of immigration (compared with 54% of the general public).
2. Underlying this distinctive attitudinal profile of supporters for both causes is a distinctive ethno-racial profile. Supporters of Trump are disproportionately "white." In fact, Trump has consistently led among those who classify themselves as "white" in polls by a margin ranging anywhere between 10% and 20%. By contrast, Clinton has consistently led amongst those who classify themselves as "black" by over 80%. Interestingly, though Clinton remains the solid favorite amongst those who classify themselves as "Hispanic," her margin of victory fell from over 50% in the middle of July to around 30% by mid-October. Likewise, supporters of Brexit disproportionately classify themselves as "white." According to the same Lord Ashcroft poll, 53% of "whites" supported Brexit, compared with only 33% of those who classified themselves as "mixed race" or "Asian," and only 27% of those who classified themselves as "black."
3. So too is there an important similarity in terms of levels of education. Those who oppose Trump and those who oppose Brexit have higher levels of formal education. Indeed, Trump has consistently trailed Clinton by somewhere between 20% and 30% amongst those with post-graduate education, and by between 10% and 20% among those with University degrees. By contrast, in mid-October, Trump led among those who had attended some college by 15%, though amongst those with a high school education or less, Clinton held a narrow 6% advantage. Meanwhile, in Britain, the relation between levels of formal education and support for Brexit was even starker. According to a pre-referendum yougov poll, support for remain was 40% higher amongst those with a university education than was support for Brexit, whereas support for Brexit outweighed support for remain by fully 36% amongst those with a highest qualification of GCSE or lower.
4. In terms of social class proper, the story is more complicated for Trump supporters than it is for Brexiters. In August, Jonathan Rothwell and Pablo Diego-Rossell from Gallup published a paper in which they found that though Trump's supporters are less educated and more likely to be employed in blue-collar jobs, they earn relatively high household incomes (thereby partially confirming Nate Silver's dismissal of claims about the working class base of Trump supporters as a myth). In Britain, however, the relation between social class and support for Brexit is clearer. According to the same yougov poll, support for remain outweighed support for Brexit by 24% amongst those in the highest social class (AB), and by 10% by those in C1, whereas support for Brexit outweighed support for remain by 20% amongst those in C2 and 26% in DE.
5. Another demographic similarity between supporters of Trump and of Brexit is age. Both causes are least popular amongst the youngest segments of the population. In the US, in mid-October, Trump led Clinton amongst those over 65 by 2% and amongst those between 40 and 65 by 5%, whereas he trailed Clinton by fully 24% amongst those under 40. But again, the relation is starker in the UK than it is in the US. Support for remain outweighed support for Brexit by fully 46% amongst those between 18 and 29 and by 24% amongst those between 30 and 39, whereas support for Brexit outweighed support for remain by 4% amongst those between 40 and 49, by 10% amongst those between 50 and 59, and by 26% by those 60 and above.
6. A final similarity in support for Trump and support for Brexit is the relatively high degree of regional concentration. An informative article by Derek Thompson published in the Atlantic during the primaries found that Trump supporters were most concentrated "in parts of the country with high degrees of racial resentments." In Thompson's words: "Find a map of the United States and draw a thick red mark just east of the Mississippi and Ohio Rivers. That's Trump Country". Likewise, support for Brexit is highly concentrated. As the BBC reported on the day after the referendum, "the Leave campaign triumphed right across England and Wales, winning in large northern cities including Sheffield, the Welsh valleys, across the Midlands including Birmingham, and the south and east of England." By contrast, "the Remain campaign dominated in London, Scotland and Northern Ireland".
7. The most significant demographic difference in the profiles of Trump and Brexit supporters has to do with gender. Gender is an important factor in explaining support for Trump. Clinton has consistently led by between 10% and 20% amongst women, and a clear majority of women register support for the claim that Trump has no respect for women. By contrast, gender does not seem to have been a factor in explaining support for Brexit.
8. A second significant difference in the profiles of Trump and Brexit supporters has to do with party identification. Only 8% of those who identify as Democrats register support for Trump, and 83% of those who identify as Republicans support him. By contrast, the partisan divide in Britain over Brexit, although significant, was much less stark. 58% of Tory voters supported Brexit, compared with 42% of Tory voters who supported remain. Meanwhile, 63% of Labour voters supported remain, though a far from insignificant 37% supported Brexit.