Donald Trump completely beclowned himself in a recent interview with The Washington Post. Even by his standards, it was a pretty embarrassing display of policy ignorance — though it probably played little or no role in his double-digit loss to Ted Cruz in Tuesday's Wisconsin primary.

But it should have. This was perhaps the low-light: At one point, Trump promised to pay off the entire $19 trillion national debt by the end of his second term as president. But doing that — while also keeping promises to cut taxes, increase defense spending, and leave Social Security and Medicare untouched — would require Trump to somehow juice the economy so that it grew by a magical 25 percent a year, according to the newspaper's analysis.

Economicus growthus leviosa!

That 25 percent figure is roughly eight times higher than the U.S. economy's average growth rate since World War II. To get to 25 percent, you're basically talking about a Star Trek economy of machine superintelligence, nanotechnology, and almost infinite abundance. Science fiction bordering on science fantasy. Indeed, as one budget analyst told the Post, "It's more consistent with a world where we're hiring butlers for our vacation homes on Ganymede."

Donald Trump, the post-Singularity candidate. Perhaps his U.S.-Mexico border will be a deflector shield or maybe an artificial wormhole that will automatically transport illegal immigrants back to their home countries.

But hey, Trump gonna Trump. He shouldn't be the standard by which voters judge the knowledge, experience, and competency of the other candidates. It's not a very high bar, after all.

Then again, if voters don't care, why should the candidates? Maybe the lesson of Trump's improbable ascent is not to bother with reason and data-driven policy positions.

Take Wisconsin-winner Bernie Sanders, someone treated — at least by the media — as a more serious thinker than Trump. But a recent Sanders sit-down the New York Daily News showed an almost Trumpian lack of policy knowledge and intellectual curiosity. When asked about trade, Sanders — as Trump does — decried the loss of U.S. manufacturing jobs to lower-cost nations from "bad deals" and "disastrous trade policies." Yet research suggests most — maybe 80 percent or more — of the decline in U.S. manufacturing jobs has been because of higher productivity and automation. Indeed, even as employment has fallen over the decades, manufacturing output has increased. Nor does Sanders seem to have much idea of how to get those jobs back or stop others from leaving. Would he, like Trump, ban companies from offshoring and outsourcing unless poorer nations paid workers more?

Of course, that can't happen. They're poor countries. And the only way they can broadly raise incomes and living standards is through trade and investment, which Sanders and Trump oppose. Or do only the American poor matter? How would Sanders help the global poor if not through capitalism? Yet it has been capitalism, not wealth taxes and redistribution, that has reduced extreme global poverty by a billion people since 1990.

Trade was hardly the only issue Sanders struggled with. He wants to break up the megabanks, but is fuzzy on how to make that happen, or if there might possibly be any downsides or unintended consequences. He says Wall Street's business model is "fraudulent" and executives should be prosecuted, but isn't quite sure for what crimes. He wants drone attacks to kill terrorists — not innocent people — but only says the "mechanism" needs to somehow be "refined" to avoid collateral damage. Sanders was also weak on his core issue of inequality, blaming only corporations and their attempts to "destroy trade unions." Yet inequality has been rising across advanced economies, suggesting broad macro forces — such as technology — may be playing a key role.

On many issues — abortion being one recent example — Trump doesn't seem to know what the policy arguments are. He just sort of reacts and says stuff off the top of his head. Sanders is a bit better, maybe. He perhaps understands his own left-wing argument, but not opposing ones from the center or right. And maybe that's unnecessary if your opponents are merely lackeys for Big Business. But it's hard to really understand a problem or know what to do about it if you don't know all sides. Even populist politicians should know a little something about policy.