Ten years ago today, Donald Trump said he would pay off the national debt in the span of just eight years.

That did not happen. Instead, the gross national debt has doubled since that day—from about $19 trillion to over $39 trillion. Much of that additional borrowing has taken place during Trump's five-plus years in the White House.

The gap between Trump's outlandish promise and the brutal fiscal reality of the past decade is not just a political gotcha. It's also an apt illustration of how far and how fast the debt has spiraled. And it's a painful reminder of a missed opportunity that Americans will be facing for a long, long time. The bill for these 10 years of fiscal profligacy will be coming due long after Trump has finally departed from the political scene.

But it's a story that starts, as everything in politics seems to these days, with Trump.

"We're not a rich country. We're a debtor nation," is what then-candidate Trump told The Washington Post in an interview on March 31, 2016 (a full transcript was published two days later). "We've got to get rid of the $19 trillion in debt."

How long would it take to do that, asked the Post's Bob Woodward.

"Fairly quickly," Trump replied. When pressed for a more specific answer, Trump provided a shocking timeline. "Well, I would say over a period of eight years."

That was never going to happen. As the Committee for a Responsible Federal Budget (CRFB) pointed out shortly after Trump's comments made headlines, "achieving this goal would be virtually impossible—particularly for a candidate who has proposed large tax cuts and ruled out significant entitlement reforms."

Instead, the CRFB estimated that Trump's proposals would cause the national debt to nearly double within 10 years. The group arrived at that figure by taking the existing baseline for the debt—which, as of early 2016, was expected to grow to about $28 trillion by 2026—and adding the estimated cost of Trump's various campaign promises.

It's worth appreciating how remarkably accurate that assessment turned out to be. The number-crunchers at the Congressional Budget Office and the CRFB didn't know there would be a pandemic. They didn't know the outcome of the major tax-and-spending bills that Trump and President Joe Biden would pass. Heck, they didn't even know who would be president—remember, in April 2026, most of the political class didn't believe Trump had much of a chance.

The accuracy of that prediction points to two things, Marc Goldwein, senior policy director at the CRFB, said when asked about it this week. First, the extent to which rising debt was baked into the federal budget before Trump came on the scene. Social Security and Medicare are the largest federal programs, and both were on pace to borrow more during the 2020s.

Second, it's due to Trump keeping many of his campaign promises. That's not the compliment that it might sound like. Trump vowed not to touch the aforementioned entitlement programs that were driving borrowing to new heights, and he promised to both cut taxes and increase military spending. That was a recipe for higher deficits, and over his first four years in office, Trump added over $8 trillion to the national debt that he'd once sought to "get rid of."

Biden picked up where Trump left off, adding another $4.7 trillion to the debt with various proposals. In his first year back in the White House, Trump has done nothing to address the growing pile of debt. The federal government borrowed $1.8 trillion during the fiscal year that ended in September and is on pace to borrow about the same amount this year.

What have Americans gotten from a decade of heavy borrowing that doubled the size of the debt? Higher inflation and higher interest rates, for starters.

A recent analysis from the Yale Budget Lab found that federal borrowing since 2015 has contributed to rising yields on long-term Treasury bonds. Those increases, in turn, have put upward pressure on interest rates and will, in the years ahead, make it more difficult for Americans to finance homes, cars, and other things.

For a typical 30-year mortgage, borrowing costs today are about $2,500 higher annually than they would be in the alternate reality where federal borrowing didn't explode in the past decade, the Yale Budget Lab estimates. Similarly, the average car loan costs $120 more annually, and the average small business loan costs $770 more.

Meanwhile, Americans will also face higher taxes or reduced government services to pay for the debt. Interest payments on the national debt will exceed $1 trillion this year—about 20 percent of all tax collections.

There are a few lessons that might be taken from all this.

First, trust the budget wonks more than the politicians. Trump's promise to pay off the national debt might be an all-time whopper of an impossible campaign promise, but he's certainly not the first or last politician to make an unrealistic claim about fiscal policy. The next time it happens, pay more attention to what the CBO or the CRFB says than anything else.

To that end, I asked Goldwein for a realistic goal that a prospective presidential candidate should set for the country.

The key, he said, is to keep the debt from growing faster than the economy as a whole, which it has been doing recently. Capping budget deficits at 3 percent of gross domestic product would stabilize the debt and put needed constraints on future borrowing.

Second, when it comes to Trump, the claim he made 10 years ago to the Post remains an illustrative example of how he engages in politics. Saying he could pay off the national debt in eight years was a ridiculous, grandiose promise made off-the-cuff without any semblance of a plan or even the intention to follow through on it.

That seems particularly relevant right now, as the Trump administration tries to figure out the next steps in a war with Iran that it launched in a similar grandiose, improvisational manner.

Trump has been making it up as he goes for a decade now, and Americans will be left to pay the price.

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