Donald Trump's tax plan makes impossible promises. This cartoon explains.

During the primaries, Donald Trump had a tax proposal that was wildly irresponsible. It included massive tax cuts, without much of a plan to spend less.

Now that he's one step closer to actually having to do the job, he has honed a slightly more realistic plan.

But that's like saying a flying unicorn is impossible so you'll settle for a regular unicorn.

We expect conservative nominees to propose tax cuts and spending cuts, and those two things are usually somewhat proportional. But even the revision of Trump's plan is not really feasible, unless he wants to balloon the national debt by $5.3 trillion. To be clear, Hillary Clinton's plan would also add to the national debt — but only by $200 billion, according to an analysis by the Committee for a Responsible Federal Budget.

To put these dollar values in perspective, we decided to do a thought experiment: If we forced the candidates to balance their budgets, what government programs would they need to cut? A quick preview: We won't be able to just trim government programs to get Trump back to even; we're going to have to get rid of entire government agencies.

Clinton would add $200 billion to the debt. Trump would add $5.3 trillion.

In the cartoon below, let's say that being at ground level is where we are now: paying for government expenses that currently exist, while adding additional expenses to the national debt. That's President Barack Obama:

But Clinton and Trump want the federal government to spend a different amount than we currently do — and collect a different amount from taxpayers.

Over the next 10 years, Trump wants save money by spending $1.2 trillion less than we are spending with Obama.

Hillary Clinton wants to spend $1.65 trillion more, which puts her in the proverbial hole.

But in that period, Trump wants to collect $5.8 trillion less in taxes, which means federal revenue would fall into a deep hole.

Clinton wants to collect $1.5 trillion more, which would almost get her to a balanced budget.

Once we add in interest, Trump would be $5.3 trillion in the hole and Clinton would be $200 billion in the hole.

Let’s do an experiment! Let’s help them balance their budgets by cutting government programs.

The Congressional Budget Office puts out a list of potential government program cuts, which calculates how much money each option would save over 10 years. So let's try to get these candidates to ground level. What if we:

• Severely reduce Pell Grant funding, which helps poor students afford college ($140.5 billion)
• Don't purchase nearly 2,500 fancy fighter jet planes that are being newly developed (F-35 Joint Strike Fighters) and instead purchase planes already in production ($31.4 billion)
• Stop building new aircraft carriers ($11.8 billion)
• Cut down on the number of ballistic missile submarines in operation ($14.9 billion)

That gets Clinton to ground level, but it barely gets Trump closer to the surface. Let's try a few bigger cuts for Trump:

• Stop human space exploration ($76.9 billion)
• Reduce funding for highways ($82 billion)
• Get rid of subsidies for Amtrak ($13.5 billion)
• Reduce international affairs programs — diplomatic, consular, and global health-related, among others — by 25 percent ($109 billion)
• Eliminate all subsidized loans for undergraduates ($38.6 billion)
• Raise the retirement age for Social Security. The younger you are, the more it would go up. For those born in 1977 or later, the new retirement age would be 70 ($34.8 billion).
• Reduce Social Security benefits by 15 percent for people newly eligible for them ($204 billion)

These are huge cuts that would virtually cripple entire agencies and shut down entire programs. But even that wouldn't help Trump get to ground level.

This isn’t working. Let's try another method.

Let's start over for Trump, back at being $5.3 trillion in the hole…

And let's cut entire agencies instead of making realistic cuts.

Let's cut all funding for transportation — for highways, mass transit, and aviation, among other things — which would save about $1 trillion for the next 10 years.

And let's cut funding for veterans, which pays for things like their health care, compensation, pension, education, and housing. That saves about $800 billion.

Let's also eliminate US consulates, embassies, military assistance to allies, aid to developing nations, and international peacekeeping efforts. That saves about $650 billion.

That only gets Trump halfway out the hole.

Let's eliminate environmental protection programs, which would save about $400 billion over the next 10 years.

And let's cut all federal justice programs — like the FBI, federal courts, drug and firearm enforcement, and federal prisons. That would save about $600 billion.

Let's also cut all of NASA, the National Science Foundation, and all other science, space, and technology programs. That saved $350 billion.

Nope, still not there.

Let's cut all income security programs, like food stamps and benefits to retirees. That would save $737 billion.

Let's cut all funding that allows the executive and legislative branches to function. That will save about $200 billion.

And let's cut all about half of the federal funding for education, social services, and the arts. That'll save about $500 billion.

Now, finally, Trump is back at ground level — after having cut all funding to crucial government programs that make the country function properly:

The kicker: Trump claims he will lower the debt

This was an absurd thought exercise, largely because Trump's tax and spending proposal are not even close to adding up.

The US could technically adopt Trump's plan and add the additional costs to the national debt. But that would balloon the debt to $28.4 trillion in 10 years, which projects out to 105 percent of GDP.

Oh, and here's the kicker: Trump has specifically said that he will lower the national debt — by negotiating it down.

So if he doesn’t propose adding to the debt, and he’s not going to cut additional spending, where does the money come from? The chart below summarized both candidates’ tax plans, and it shows that Trump can’t stick by his tax plan and lower debt.

With this logic, if Trump were a kid who owned a lemonade stand, he would slash prices, buy slightly worse lemonade, and somehow make more money than before to pay back his dad for giving him the wood to build the stand. Maybe to Trump, these promises are “all words” and “sound bites.” But these promises also include numbers, and all the talking in the world won’t make these numbers add up.

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