This week, former Texas congressman and Democratic presidential candidate Beto O'Rourke proposed a war tax. The proposal represents the most radical antiwar policy of anyone vying for the Democratic nomination in 2020.

O'Rourke's proposal is logistically pretty simple. When a new war is authorized, a tax would automatically go into effect to help pay for it. The tax would be levied on all families "without current members of the Armed Forces or veterans of the Armed Forces," and it would be progressive. Households making more than $200,000 would pay $1,000 a year. Those making less than $30,000 would pay $25 a year. The proceeds from the tax would go into a fund to support veterans health care.

There has been plenty of initial skepticism of O'Rourke's plan, especially among young progressives. A common concern is that the tax would become primarily a new funding mechanism for war.

There has been plenty of initial skepticism of O'Rourke's plan, especially among young progressives. A common concern is that the tax would become primarily a new funding mechanism for war and war's consequences. Alex Pareene, a staff writer for The New Republic, for example, tweeted that "an actually good war tax would raise the top marginal rate 10 points for each new war." Similarly, Ken Klippenstein, a reporter for The Young Turks, tweeted that we should have a war tax on defense contractors rather than on "working people for wars the vast majority of them never supported."

In part, this opposition is O'Rourke's fault. By framing the war tax as part of a veterans health bill, he obscured its radical potential to change the political calculus around foreign intervention. This makes it seem like the war tax is a domestic spending proposal, rather than as a frontal assault on the foreign policy establishment.

Nonetheless, it is in fact a potentially transformative foreign policy proposal. Currently, wars are financed through debt and borrowing. Most people therefore don't feel the effects of these conflicts in any direct concrete way. A war tax would change that, as Sarah Kreps, author of "Taxing Wars: The American Way of War Finance and the Decline of Democracy," explained to me. "If people were forced to pay the cost of war, they would make some sort of calculation in their minds about whether the war being fought is worth the fiscal sacrifice they're making," Kreps says. "And as soon as those are no longer in alignment, they would start putting pressure on leaders to find a suitable end to the war."

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Kreps has data to back this up. In 2017, she and Cornell government professor Gustavo A. Flores-Macías published a paper in the Journal of Conflict Resolution examining the link between support for war and the method by which the war was financed. They conducted a public opinion survey of 2,500 adults in the United States and 2,122 in the United Kingdom in June 2013.

Their results were striking. Wars financed by borrowing alone were 8 to 12 points more popular than wars financed by borrowing and taxes. More, this effect held regardless of partisanship. In the U.S., both Republican and Democratic support for war fell when the public was directly taxed to support the conflict. Partisan differences were not significant.

Twelve points is a significant gap. That means that a war that had 55 percent support could drop to only 43 percent if a war tax were attached. More, as Kreps pointed out, imposing specific taxes for unpopular projects tends to have volatile results. A new fuel tax in France to control climate emissions inspired violent protests just last year. A war tax, if instituted, could plausibly inspire very strong reactions in Americans the next time war is declared.

The biggest problem with O'Rourke's war tax is that it would be virtually impossible to pass. This is not because of progressive opposition, however.

The biggest problem with O'Rourke's war tax is that it would be virtually impossible to pass. This is not because of progressive opposition, however, but because politicians are very reluctant to face public scrutiny on military issues. When New York Democratic Rep. Charles Rangel called for a war tax in 2014, it went nowhere.

Currently, presidents have a lot of leeway on military issues. Unless they lose a major war, as President George W. Bush did in Iraq, they and their party face few electoral consequences for missteps. Trump's war in Yemen is so unpopular that he had to override a Congressional veto to continue to pursue it. But going into 2020, according to Pew, the military is only the fifth most important issue facing America for Republicans, and isn't in the top five for Democrats. With a volunteer army and costs hidden in long-term borrowing, most Americans have little visceral investment in shutting down wars, even when they don't like the wars in question.

Politicians hate facing consequences, and so it's in every politician's interest to preserve a status quo in which Americans don't hold presidents or Congress responsible for military policy except in the most extreme cases. Even Democratic presidential hopeful Sen. Bernie Sanders, who has made a strong argument for a less interventionist, less war-happy foreign policy, has been light on details. He's called for cuts in military defense, for example, but hasn't set specific targets.

Presidents Barack Obama and Donald Trump both made promises to restrain intervention, too. Both ended up with often aggressive military policies driven by a vast military industrial complex and a default political calculus that doing something looks more impressive than doing nothing.Even Sanders as president would likely have trouble defying those institutional incentives.

That's why O'Rourke's proposal is so important. A war tax isn't a personal promise to be less interventionist. It's a policy designed to change the calculus for all politicians. And it challenges other Democratic candidates to develop specific counterproposals. If you don't want a war tax, what would you offer instead? By how much would you cut the defense budget, and what would you do with the reallocated funds? How could we strengthen the War Powers Act, which Sanders was able to leverage in the Senate to condemn the war in Yemen? How do you spread the costs of war more equitably so that the public can no longer ignore them while soldiers, veterans and people overseas suffer?

The Democrats are having a vigorous and exciting debate in the primary about domestic policy. We need the same kind of discussion about military intervention and war. O'Rourke has taken the first step in that direction. His messaging and ideas may not be perfect. But he should be commended for recognizing that the best way to honor veterans is to try to ensure that, in the future, fewer people will have to fight.