Maybe last week wasn't the week to start watching Amazon's dazzling new screen adaptation of Philip K. Dick's "The Man in the High Castle." Or maybe it was.
Dick's 1962 novel imagines a fascist America — or, to be precise, an America partitioned between the Axis powers after a Second World War that has ended in defeat for the Allies. The east of the country is under the thumb of Nazi Germany; the Western states are colonies in the Japanese "co-prosperity sphere."
Like Philip Roth's more recent book "The Plot Against America" — which imagines a Nazification from within after the pro-Hitler aviator Charles Lindbergh becomes president in 1941 — this nightmare vision is compelling precisely because it has what the comedian Stephen Colbert calls "truthiness." We know it didn't happen. But we can (with a shudder) imagine it.
After all, the fate of defeat and occupation by the Axis powers was suffered by a great many countries. And there was no shortage of American sympathizers with the Nazis. On Sept. 11, 1941, in a speech in Des Moines, Iowa, Lindbergh accused "Jewish groups in this country" of "agitating for war."
Two years earlier a Fortune magazine poll had asked: "If you were a member of Congress, would you vote yes or no on a bill to open the doors . . . to a larger number of European refugees?" Eighty-five percent of Protestants and 84 percent of Catholics answered no.
So here we are again.
Like Lindbergh, Donald Trump combines racism with isolationism. He wants to make America "great again" by keeping it out of foreign wars. And, like the far right of the 1930s, Trump also wants to keep out refugees on religious grounds. Last Monday, responding to the San Bernardino massacre, he called for a "total and complete shutdown of Muslims entering the United States."
Time and again this year I have been told that Trump has jumped the shark. Yet the latest national CBS News/New York Times poll shows that he has the support of 35 percent of Republican primary voters, far ahead of his nearest rival, Ted Cruz.
What is going on? The conventional answer is that many Americans, dismayed by their deteriorating economic prospects, are experiencing a surge of populist rage — much like National Front voters in France. But it is not immediately obvious that standard economics can explain this. Unemployment in France is twice as high as it is here.
A second answer is that this is a revolt against widening inequality — an argument bolstered by the news that, for the first time since 1970, middle-class households are outnumbered by lower- and upper-class households. Yet people do not become racists just because they drop out of the middle class.
The nearest thing to an answer I can find is in an astounding new paper by the Nobel laureate Angus Deaton and Anne Case, which exposes what can only be called an existential crisis of white America — to be precise, badly educated white America.
All over the Western world mortality rates are declining and lifespans are lengthening. But not in white America, and especially not among those white Americans whose education didn't go beyond secondary school. For this group, the mortality rate from poisonings (mostly drug overdoses) rose more than fourfold between 1999 and 2013, from 14 to 58 per 100,000. Mortality from chronic liver diseases including cirrhosis rose by 50 percent.
If the white mortality rate had continued to fall at its pre-1999 rate of 1.8 percent a year, nearly half a million deaths would have been avoided in the period 1999-2013.
The white underclass is not so much mad as hell as sick as hell. One in three white people aged 45-54 report chronic joint pain, one in five neck pain, and one in seven sciatica. Presumably, it's the most miserable who drug or drink themselves into early graves. The rest just exit the workforce, opting for disability benefits. Small wonder labor force participation in America has declined so steeply, even as it has risen in other developed countries. Small wonder Trump is polling so well. He is the sick people's sick candidate.
"The Man in the High Castle" is fiction, not history. The Axis powers could never have beaten America, even with a president inferior to Franklin Roosevelt. In the end Trump will turn out to be fiction, too. Either sanity will prevail between now and the Republican National Convention, or Trump will be beaten by Hillary Clinton, much as Wendell Wilkie (another maverick businessman) was beaten by Roosevelt in 1940.
The lesson of real history is that candidates such as Trump are the Democrats' best friends.
Niall Ferguson is professor of history at Harvard and a senior fellow of the Hoover Institution, Stanford.