In a fearful and angry political season, it may be only natural that trade and immigration are together dominating America's presidential campaign debate.

Whatever the differences between these issues, both are about blaming foreigners for many of the nation's problems — a handy export market since we seem stuck with a surplus of resentments to unload on somebody.

Just now, decrying unfair trade, unpatriotic corporate globe-trotting or uncontrolled immigration also gives people of quite diverse ideological leanings the same reassuring sense that they understand rather more than they do.

There is almost a kind of innocent hopefulness about the bipartisan xenophobia of 2016. Wouldn't it be lovely, after all, if simply slamming some or all of our national doors on the outside world could cure what most ails America today — the undeniable distress of lower-skilled working-class Americans and the lasting stagnation of even middle-class incomes?

There are notable differences on these issues, of course, between Hillary Clinton and Donald Trump. One of them is ignorant, the other merely incoherent. One doesn't know what he's talking about; the other may not mean what she says.

Both candidates would insist that their positions involve subtleties, and maybe they do. But at root Trump portrays both immigration and trade (including U.S. firms "offshoring" jobs) as economic threats forcing American workers to compete with low-wage rivals (he sees dire criminal and terrorist threats in immigration, as well).

Clinton, meanwhile, portrays immigrants (including illegals already here) as an unqualified boon to the U.S., while increasingly arguing that trade and offshoring undercut U.S. workers' well-being.

Trump, heaven help us, wins the points for consistency here. If a low-wage worker in China assembling a product for shipment to America is an economic threat we must confront, then so must be the illegal Mexican immigrant in our midst filling a job (or two) that some American might otherwise hold. How could one "foreign" worker be purely an asset if the other is purely a problem?

Many progressives may fail to see the parallel simply because the nearby immigrant is visible, undeniably human and real, in a way the remote foreign workforce is not.

But one doubts, somehow, that Clinton is confused in this way. More likely, she has once more braved inconsistency and has remade herself as a protectionist, turning her back on her (and her husband's) political lifetime as free-trade advocates, only because the feverish politics of vanquishing Bernie Sanders required it. Without making off with the nomination, Sanders has in this disfigured the Democratic agenda rather as Trump has deformed the GOP creed.

It's likely that Clinton's extensive international experience means she sees more clearly than most American politicians what none of them dare to say: That the benefits of free trade we should celebrate most assuredly include its benefits to those mysterious yellow and brown workers in China and Bangladesh and Uruguay and a hundred other countries — hundreds of millions of whom have been lifted out of the worst depths of poverty in recent decades through engagement with the world economy.

Unfortunately, the damage likely to come from the ruinous 2016 campaign may well include a sharp reversal for the cause of free trade. It is hard to imagine new trade-boosting agreements — always a hard sell — being negotiated anytime soon after this bipartisan anti-trade tirade — and easier to foresee existing ones being abandoned.

The Trans-Pacific Partnership is almost certainly dead. It was the Obama administration's chief trade initiative, lowering trade barriers with 11 Asian nations as part of a broader foreign-policy "pivot" to counter China's growing influence and ambition.

Economists have long despaired — for centuries really — over their inability to convince most people of what nearly all of them consider a basic truth — that over time and overall, the free flow of goods, services, ideas, capital and people makes us all better off.

The Trumpian notion that a nation either "wins" or "loses" in trade is an aged fallacy. Trade involves competition, of course, but as in domestic commerce it is companies and workers that profit or falter, not governments or communities. Society as a whole prospers over time because competition (domestic or international) leads to better goods being offered at better prices.

To "protect" companies or workers from foreign competition (except where true unfair distortions are involved) is to deny everyone else access to better quality and/or lower cost products.

It's true that workers in particular sectors can be hit hard with trade- or immigration-related job losses or wage declines. It happened notably to steel and autoworkers a generation ago and to broader manufacturing workers with the normalization of China trade in the 1990s.

But over time, given America's enormous domestic market, technological change and automation is the far larger disruptive force eliminating jobs and forcing difficult adjustments on workers in an ever-expanding array of fields.

Above all, it is all this combined with what is now clearly an era of slower economic growth over nearly a half-century that is producing an age of anxiety and discontent in America's working class.

We need a thoughtful debate about this poorly understood economic reality — what we can do to change it, and what we may need to do to adapt if we're stuck with it.

But cutting off trade or immigration won't help.

D.J. Tice is at Doug.Tice@startribune.com.