The GOP presidential nominee is out on the trail ahead of the general election in November.

The GOP presidential nominee is out on the trail ahead of the general election in November.

What Donald Trump is doing on the campaign trail

What Donald Trump is doing on the campaign trail

Americans — or, at least, a particular subset of Americans — have had enough of experts, facts, math, data. They distrust them all.

This rising cynicism, sown recklessly by opportunistic politicians, will not only make it increasingly difficult for policymakers to make good choices and govern peacefully; it could also become a significant economic challenge.

The latest evidence of this anti-evidence trend comes from a Marketplace-Edison Research Poll released last week.

The survey found that more than 4 in 10 Americans somewhat or completely distrust the economic data reported by the federal government. Among Donald Trump voters, the share is 68 percent, with nearly half saying they don’t trust government economic data “at all.”

You know those unemployment rates, inflation numbers, household spending figures, health insurance coverage rates, gross domestic product growth and other stats that companies and consumers rely on when making financial decisions? Nearly half of Americans, and a supermajority of Trump voters, believe the books are cooked.

And based on the “shadow stats” and inflation truther movements, most data skeptics seem primed to believe this book-cooking is meant to make the economy look stronger, and President Obama look better, than either truly is.

One risk of this apparently widespread suspicion is that it could become self-fulfilling. If enough people and businesses believe the economy is secretly terrible, they will behave in ways that make it terrible — by curbing their own spending and hiring, for example.

This distrust of public data is partly, though not entirely, Trump’s fault.

Republican presidential nominee Donald Trump believes there's a global conspiracy to stop him from becoming president – but it's not the first time he's pushed unfounded theories. (Peter Stevenson/The Washington Post)

At times Trump has mused that “real” unemployment is as high as 42 percent , a comically hyperbolic figure. Such comments are part of his broader narrative of numerical nihilism, a political strategy of discrediting any statistic or fact that could obstruct his path to the presidency.

Faced with poll data showing that the Republican nominee is losing ground, for example, Trump and his supporters claim that the surveys are skewed, that the reported results are just pro-Hillary Clinton propaganda, that rally crowd size is a much better predictor of an Election Day victory, la la la I can’t hear you.

Unflattering assessments of Trump’s policy proposals receive similar treatment.

Offered sober-minded, nonpartisan analyses that Trump’s fiscal plans would add trillions to deficits and jeopardize the economy, his supporters claim these assessments must be lies because (A) the analysts are biased against him, and (B) Trump would obviously never let bad things happen to the economy, duh.

In other words, ignore the experts, ignore the math, trust the message.

Or as World’s Worst Surrogate Ben Carson said Friday on MSNBC, “Let’s throw the economists out, and let’s use common sense.” Presumably Carson believes that all forms of expertise, including neurosurgical, should be similarly disposed of in favor of “common sense.”

This paranoid anti-evidence trend long predates the current election, of course.

There was also a poll “unskewing” cottage industry in 2012, when supporters of Mitt Romney were convinced their candidate would win the White House handily. Then, as now, large rally crowds were cited as evidence that pollsters simply had to be wrong.

Why do voters continue to buy this nonsense?

Yes, there are certainly times when experts and number-crunchers get things wrong; and yes, there is a fundamental numeracy deficit in this country.

But this anti-intellectual, ignore-the-data attitude mostly owes its growth to a careless, conspiracy-theorizing league of (mostly) conservative politicians and pundits. They elevated themselves by sowing distrust in traditional institutions and sources of authority, from the media to civil servants to scientists. They presented themselves as the sole truth-tellers, system de-riggers and messianic statistics unskewers, while maintaining that everyone else was feeding the public lies.

Today, some of these same message-bearers are the victims of their own success. The most prominent right-wing media outlet, Fox News, has been attacked by even more right-wing media outlets for supposedly conspiring against Trump. Fox News’s own polls, for example, stand accused of pro-Clinton skewing.

And many of the politicians who rose to power on their anti-establishment, anti-politician, anti-government, anti-evidence bona fides now find themselves in the cross-hairs of an even more anti-all-those-things outsider candidate.

The problem with elevating yourself by tearing down the existing authoritative institutions is that once you succeed, you’ve established a road map for others to tear you down, too. There will always be someone waiting in the wings with an even juicier conspiracy theory, an even zanier hidden truth, an even more intricate data-unskewing method — and there’s no longer any authority left to debunk any of it.

This is how a democracy crumbles: not with a bang, but with data trutherism.