You often hear that in these polarized times, Republicans and Democrats are deadlocked on almost everything. But the real scandal is what both sides agree on.

The best example of this might be the defense budget. Last week, the Democratic House, which Republicans say is filled with radicals, voted to appropriate $733 billion for 2020 defense spending. The Republicans are outraged because they — along with President Donald Trump — want that number to be $750 billion.

In other words, on the largest item of discretionary spending in the federal budget, accounting for more than half of the total, Democrats and Republicans are divided by 2.3 percent. That is the cancerous consensus in Washington today.

America’s defense budget is out of control, lacking strategic coherence, utterly mismanaged, ruinously wasteful and yet eternally expanding. Last year, after a quarter century of resisting, the Pentagon finally subjected itself to an audit — which itself, in true Pentagon style, cost more than $400 million. Most of its agencies — Army, Navy, Air Force, Marines — failed. “We never expected to pass,” admitted then-Deputy Defense Secretary Patrick Shanahan.

The Special Inspector General for Afghanistan Reconstruction has identified $15.5 billion of waste. But that is after reviewing only $53 billion of the $126 billion appropriated for Afghan reconstruction through 2017. He wrote in a 2018 letter, “[We] have likely uncovered only a portion of the total waste, fraud, abuse and failed efforts.”

Outside war zones, there are the usual examples of $14,000 toilet seat lids, $1,280 cups (yes, cups) and $4.6 million for crab and lobster meals. Remember when then-Secretary of Defense Robert Gates noted that the Pentagon had about as many people in military bands as the State Department had active foreign service officers? Well, it’s still true today.

Trump says he is a savvy businessman. Yet his attitude toward the Pentagon is that of an indulgent parent. “We love and need our Military and gave them everything — and more,” he tweeted last year. Far from bringing rationality to defense spending, he has simply opened the piggy bank, while at the same time trying to slash spending on almost every other government agency. The Pentagon is the most fiscally irresponsible government agency, but the Republicans’ response has been to simply give it more.

The much deeper danger, however, is spotlighted by Jessica Tuchman Mathews in a superb essay in the New York Review of Books.

Mathews points out that we tend to think about the defense budget as a percentage of the country’s gross domestic product, which is fundamentally erroneous. The defense budget should be related to the threats the country faces, not the size of its economy. If a country’s GDP grows by 30 percent, she writes, it “has no reason to spend 30 percent more on its military. To the contrary, unless threats worsen, you would expect that, over time, defense spending as a percentage of a growing economy should decline.”

The United States faces a world in flux, to be certain, but surely not a more dangerous world than during the Cold War. The U.S. now spends more than the next 10 countries in the world put together, six of which are close allies — Britain, France, Germany, Japan, Saudi Arabia and South Korea. And the real threats of the future — cyberwar, space attacks — require different strategies and spending. Yet Washington keeps spending billions on aircraft carriers and tanks.

There are even more fundamental questions about the structure of the Pentagon. Why do we have an Air Force if the Army, Navy and Marines all have their own air forces? Why does each service have its own representatives to essentially lobby Congress? When he was Defense Secretary in the early 2000s, Donald Rumsfeld tried to force some coherence onto the department (a legacy overshadowed by his disastrous handling of the Iraq War), but he was mostly outmaneuvered by the Pentagon and Congress. ‘’You refer to closing unneeded bases,’’ Rep. Rob Simmons of Connecticut said to Rumsfeld. ‘’I only have one base, and I do need it.” Multiply this response by 535 members of Congress to understand the depth of the problem.

Dwight D. Eisenhower was the kind of Republican who had a pragmatic skepticism about government. He was the kind of seasoned general who understood that peace came from a combination of military strength and diplomatic engagement. That was why in his presidential farewell address he spoke about the dangers of the “military-industrial complex.” Sixty years later, it looks like one of the most prophetic warnings any president has ever made.

Fareed Zakaria is a Washington Post Writers Group columnist.