ANALYSIS | To the Pentagon, its contractors and allies on the congressional defense committees — the so-called iron triangle — John McCain could be either the U.S. military’s strongest proponent or its harshest critic.

It is clear to the members of the triangle that they will miss the friend they had in the hawkish McCain. They may not fully appreciate, however, how much they will miss the enemy, too.

Congress must call out failing defense programs and battlefield snafus. The benefit to the taxpayers and the soldiers on the front lines is fairly obvious. But everyone benefits, including those who are the targets of his criticism.

McCain saved the government billions by helping stop some wasteful programs, and the fear among generals and defense executives of ending up the subject of his questions may have saved billions more.

In the war zones, the long-term effect of McCain’s hard questioning is still an open question, but the surge in Iraq that he supported steadied that war effort at least for a while.

In any event, someone in Congress needs to expose problems, or the military will be less efficient and less likely to deter or win wars. Even if McCain’s rough treatment of some of the brass or certain CEOs seemed like the last thing they needed at the time and may have hurt some bottom lines, the ultimate effect of robust oversight is more support for the Pentagon and a stronger defense.

Watch: Lawmakers Remember McCain as ‘Patriot,’ ‘Friend’

Equal-opportunity criticisms

McCain’s criticisms, whether about military programs or operations, crossed party lines, and were directed at presidents, Defense secretaries and top generals.

McCain scoured the George W. Bush administration’s Iraq war policy with a wire brush, taking particular aim at former Pentagon chief Donald Rumsfeld’s panglossian assessments. McCain was an advocate of Gen. David Petraeus’s counterinsurgency strategy, which for several years involved a so-called surge of more troops than most members of either party were willing to publicly defend.

McCain, an Armed Services member who eventually rose to the chairmanship of the powerful panel, had been similarly insistent on the need for a strategy in Afghanistan other than what he described as “don’t lose.” In Syria, McCain and his hawkish sidekick, South Carolina Republican Sen. Lindsey Graham, called for years for a larger U.S. military role than presidents from either party could stomach.

McCain also doggedly assailed congressional add-ons to the defense budget that he deemed were unnecessary. Every year, even after formal earmarks were outlawed, McCain produced “pork” lists and looked for colorful examples to deride in floor speeches.

It wasn’t just congressional pork he targeted. Despite his strong support of robust defense spending, McCain was the primary architect of several years’ worth of statutory overhauls to how the Pentagon buys its weapons.

Imperfect oversight

McCain didn’t just address the Pentagon’s procurement problem in a broad sense. He also took on particular weapons programs where technical, cost and schedule problems had spiraled out of control. He was rarely polite in his criticism.

He was a constant thorn in the side of the Virginia-class attack submarine program in the 1990s. In the 2000s, he was a pitbull in going after the Air Force’s proposed lease of Boeing tanker aircraft, an initiative that was eventually shown to be riddled with corruption. In the early days of the Obama administration, McCain led the charge against the presidential helicopter program, which he said had “run amok.”

More recently, he has excoriated the efforts to develop the F-22 and F-35 fighter jets, the Ford-class aircraft carrier, the Littoral Combat Ship and the Evolved Expendable Launch Vehicle for falling short on performance or going long on cost.

To be sure, McCain was an imperfect critic. He sometimes seemed to hector witnesses in hearings mostly for dramatic effect. He often would give a speech criticizing a program but not offer an amendment to kill its funding.

For every off-the-rails program he criticized, there were many more — such as the Future Combat Systems in its heyday, before it was killed — that he effectively signed the checks for even after experts had convincingly showed its flaws. He seemed to soften his criticism of the F-35 program after the Pentagon decided to base some of the jets in Arizona.

Moreover, McCain was perhaps too sanguine about the effectiveness of U.S. military power. On Syria, for example, while the urge to use force has been understandable, U.S. military options in that country have never been good, a problem that McCain was loath to concede.

A void left behind

In any event, McCain saw his support and his criticism as two sides of the same coin — a desire to help America’s military. It was obvious to the iron triangle that McCain was helpful when he was supportive. But it wasn’t always evident to them that the critical McCain was a good thing, too.

As McCain himself said, political support for high levels of defense spending could not be sustained unless there was progress reining in excesses. Cutting wasteful spending was important in its own right, he believed, because the money could be used more fruitfully elsewhere — elsewhere in the defense budget, that is, in McCain’s view.

America needs lawmakers like McCain who can both support the Pentagon and call it out when it errs. The question now is whether the country will get it. The answer is probably: No.

It is no slight to the current leaders of the congressional defense committees to say that they cannot fill McCain’s shoes. No one can meet that standard. He had too much courage, conscience and personality.

Democrats generally do not have the Nixon-goes-to-China credibility as critics that only a Republican skeptic of the military can bring. And those who do support robust military spending often do so because of parochial interests rather than an abiding national security philosophy.

There are a few exceptions, such as Adam Smith of Washington, but it remains to be seen how much he and others will be both willing to take on entrenched interests and able to convince Republicans to go along — the kind of bipartisanship that McCain was adept at.

Meanwhile, Republicans on the defense panels are also beholden to the iron triangle and many are loathe to criticize any defense program, for fear of forfeiting any hard-fought defense dollars. To most of them, the motto is: our military, right or wrong; instead of: our military, when it’s wrong, let’s make it right.

Without McCain, it’s hard to see who will be willing to take the necessary political risks and break the china in the years ahead.

Barring some major change, then, McCain’s departure will leave a huge gap. His brand of conviction and cojones will not soon be replicated. But some pale version of it is needed ASAP as Washington conducts its oversight, and not just of the military.