The chief reason is that, unlike the U.K., the U.S. has a large voting population of nonwhites: Latinos, black Americans, Asian Americans, etc. In Britain, “black and minority ethnic” people make up about 8 percent of the electorate. By contrast, people of color account for nearly 1 in 3 American voters. In practice, this means that in the past two national elections, there has been an electoral penalty for embracing the most reactionary elements of national life. And we see this in the polling between Trump and Clinton. If the United States were largely white -- if its electorate were as monochromatic as Britain’s -- then Trump might have the advantage."Might" is an understatemnt, as I'll explain below.
There's far less polling in the U.K. of the kind we're used to, but the Lord Ashcroft Poll tells us this about the ethnic breakdown of the Brexit vote:
White voters voted to leave the EU by 53% to 47%. Two thirds (67%) of those describing themselves as Asian voted to remain, as did three quarters (73%) of black voters."Leave" was the winner in the Brexit referendum by approximately 4 points; according to this poll, whites backed "Leave" by 6.
By contrast, a new Washington Post/ABC poll has Hillary Clinton leading Donald Trump by 12 in a two-person race, and by 10 in a four-person race (with Gary Johnson and Jill Stein) -- but this massive Clinton lead comes despite the fact that Trump leads by 10 among white voters in a two-person race, and by 12 in a four-person race. So Trump is doing much better among whites than Brexit did -- yet he's getting clobbered in the overall race.
And Trump isn't even able to take full advantage of the fact that the Republican Party is the party of Team White People: Exit polls showed in 2012 that Mitt Romney beat Barack Obama by 20 points among whites, in an election he lost overall by 4 points. In 2008, John McCain beat Obama among whites by 12 points, in an election he lost overall by 7. So Trump is underperforming those guys among whites -- he's even underperforming McCain, who ran in a year when Obama had the second-best Democratic vote percentage in a presidential election since 1944.
Does this mean Trump can't win? No -- the Post/ABC poll is somewhat of an outlier; a new NBC/Wall Street Journal poll shows Clinton up by only 5 in a two-person race, and up by 1 in a four-person race. It's a contest, according to this poll -- though he's still losing.
But what if the polls are underestimating support for Tump, as they did for Brexit? Note that the final Brexit poll average, according to Pollster, showed "Remain" leading by 0.5; "Leave" won by 3.8% But in the presidential race, poll averages suggest that Clinton's lead is solid -- Real Clear Politics says she's now up by an average of 6.7 in a two-person race and 5.6 in a four-person race. That means that even if Trump's support is being underestimated by 4.3 points, as Brexit's was, he'll still lose.
But in that case it'll be a tight race -- and yes, that will be thanks to "embattled whites," with non-whites saving us from ourselves once again.