In the weeks leading up to the election, In Theory will be asking policy experts to weigh in on the critical questions our presidential candidates should be addressing — but often aren’t. This week we’re discussing the national debt.

In the last fiscal year, the federal government spent 6 percent of its budget to service the national debt. That’s $223 billion going toward paying the interest on borrowed money — and that portion of our budget is only projected to increase as government spending expands.

There’s considerable amount of debate about whether this is actually a bad thing. After all, most Americans and businesses have some level of debt on hand. Debt allows us to buy things we can’t afford now, and that’s often a good thing — much of our national debt is the result of federal spending on programs such as Social Security, Medicare, Medicaid and defense. But the government is already wrestling with massive deficits on a year-to-year basis, so the fact that a growing chunk of its revenue immediately goes to covering its debt obligations calls into question our financially sustainability.

As secretary of state, Hillary Clinton said the debt poses a national security threat. But she’s been noticeably silent on the issue throughout her campaign. In fact, economists have projected that her campaign proposals would increase the debt over the next decade (by how much is disputed — some say as low as $275 billion, others say as high as $1.5 trillion). Meanwhile, Donald Trump has regularly campaigned on eliminating the national debt by cutting government spending — although most economists have balked at his proposals as unrealistic austerity (especially along with his proposals to massively reduce taxes).

What happens if our historically low interest rates rise in the next few years? What’s the plan if we have to spend, for example, twice as much (that’s 12 percent) of our budget on interest rates? How do we avoid falling into the so-called “debt spiral” seen in countries like Japan or Greece?