(Reuters/Rebecca Cook)

That’s the provocative thesis advanced by David Bernstein in a new piece for Politico Magazine:

If Trump wins the GOP nomination, he will be testing the limits of a strategy that has long haunted the Republican Party. Since the civil rights era, the Republicans have relied heavily upon white male voters in order to overcome a disadvantage among minorities and some subsets of women. Mathematically, that was an easier strategy a half-century ago, when white men dominated the electorate. But as the GOP failed to broaden its coalition and the demographics of America have shifted dramatically, an ever-greater percentage of white men has been required to secure a GOP victory.

And if, as it appears, Trump’s opponent in the general election is Hillary Clinton, his lane becomes even narrower….

The math suggests Trump would need a whopping 70 percent of white men to vote for him. That’s more than Republicans have ever won before – more than the GOP won in the landslide victories of Ronald Reagan and George H.W. Bush, and far more than they won even during the racially polarized elections of Barack Obama.

Click the link to see how Bernstein gets to that number. The short version is that between 1980, when Ronald Reagan won the presidency with 63 percent of the white male vote, and 2012, when Mitt Romney lost after getting 62 percent of the white male vote, the Hispanic and female shares of the electorate have soared. Winning approximately the same percentage of that demographic meant less and less over that period.

Bernstein looks at some 2016 turnout projections for Latino and female voters, and the deficit Trump might suffer among both demographics, and concludes:

Even allowing for just a typical seven percent to eight percent gender gap, that still means, as noted above, that Trump’s share of white men would need to reach 70 percent in order to capture a majority of the popular vote. That’s higher even than the 68 percent of white guys won by Richard Nixon in 1972 and by Reagan in 1984, in their respective 49-state landslide re-elections.

There’s no way to know right now whether this seven-in-10 number will prove accurate — as Bernstein notes, Trump might somehow manage to moderate if he is the nominee. But it’s reasonable to assume that Trump very well might drive nonwhites and women away from the GOP in astronomical numbers, meaning he’d very likely have to do better — perhaps much better — than Romney did among white men to have any shot.

So I took a peek at Quinnippiac’s most recent national polling, and it turns out that Trump is well short of that seven-in-10 mark. Trump beats Hillary Clinton by 57-31 among white males, and he beats Bernie Sanders by 55-35 among them. Interestingly, the other GOP candidates do around as well as Trump does against Clinton among that demographic.

Obviously head-to-head polling tells us little right now, and a thousand things can and will change between now and next fall, but this gives us at least a general sense of how steep a demographic mountain Trump would have to climb to have a shot at winning.

It’s worth noting that Republican and Democratic strategists are all thinking about these very questions right now. Politico reports today that Republican strategists are deeply worried that Trump will do precisely the opposite of what Republicans had hoped when they unveiled that much balleyhooed 2012 RNC autopsy that recommended ways of broadening the GOP’s appeal to minorities and women. Trump boosters argue that he’s broadening the party by bringing in more working class whites, but the authors of that autopsy scoff at that argument, and say he’ll drive the party into a demographic abyss.

(The party arguably set this in motion well before Trump ran for president, when Congressional Republicans shelved immigration reform rather than suffer the wrath of the right, but that’s another story.)

Hillary Clinton’s aides are also looking hard at whether her own struggles with white men, and Trump’s seeming ability to play to their anxieties, could conceivably give Trump a road to the White House that passes through the Rust Belt. As James Downie points out, Clinton has been pushed in a more populist direction by the Sanders challenge, which could help on that front. Meanwhile, as Buzzfeed reports, the Clinton camp is taking heart from her performance among rural and older white voters in certain regions on Super Tuesday, as a sign she may be able to assemble a broad general election coalition.

Ultimately, the demographic fundamentals will probably be daunting for the Donald. Trump’s swaggering xenophobia and emphasis on all things big about himself would seem to suggest he’s hoping to ride a wave of white male backlash into the White House. But Trump may end up crashing into a wall of demographic reality.

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UPDATE: I should have noted that the Quinnipiac poll also has Trump and Clinton nearly tied. The point is that if Bernstein is right about what the electorate might look like next fall — and Quinnipiac is close to right about how the white male vote will break down — then Trump would face daunting demographics. Ultimately it’s way too early to draw anything more than very general conclusions. I just wanted to plant a flag on questions that strategists on both sides are already thinking about.