Ask the White House where President Barack Obama derives the legal authority to bomb Islamic State fighters in Syria, and you’ll get a master class in handwaving. The 2003 authorization to invade Iraq fits because we’re now defending Iraq. The 2001 authorization to attack Al Qaeda fits because ISIS is a kind of outgrowth of Al Qaeda.

But many members of Congress—including Republicans, who have been so jealously guarding their checks on executive power—are perfectly happy to see Obama use military force anyhow.

They could resolve this wee contradiction in an afternoon, if they wanted, by passing a new Authorization for Use of Military Force (AUMF) in Syria. But barring some unforeseen calamity, they won’t. At least not before the election. And the reasons should make you just as annoyed with Congress as you’re probably already inclined to be.

Whether you support the administration’s actions, or think they’re foolhardy, or believe they’re unconstitutional, it’s hard to deny that they’re popular. The public understandably distinguishes between wars of occupation and regime change on the one hand, and military assaults (covert or aerial) against Islamic terrorist networks on the other. To the extent that the former was ever popular, it ceased to be almost a decade ago. The latter has been popular pretty consistently.

Obama may believe that the Constitution empowers him to bomb Syria with or without congressional authorization. But he’s mostly just behaving as if the only check on this military campaign is political. If the public were opposed, he wouldn’t have ordered the strikes—or he would have sought Congress' approval, knowing he wouldn't get it.

So if the public supports it, why wouldn’t members of Congress want a piece of their constituents' gratitude?

Because voting on the issue would violate the Optimal Preening Principle, which tends to govern these debates.

Killing terrorists, or alleged terrorists, might be popular. But it’s also something the military (and thus, the president) does. Meanwhile, on a good day, Congress votes on legislation. The president might use a new AUMF to do things the public overwhelmingly supports, but that won’t help the embattled congressperson who would have to defend granting the president unlimited warmaking power or defend voting against bombing terrorists because the AUMF wasn’t expansive enough. Instead, by not being forced to take a stance, Obama's opponents will be able to frame the issue however they want to.

Likewise, when something goes wrong—as it inevitably will—members of Congress won’t want to be linked to it with their votes, and won’t want their votes constraining them from harrumphing about it on camera. Constituents won’t credit them if things go swimmingly anyhow, so they see no upside in sticking their necks out.

The posture that allows for optimal preening is thus to offer qualified support, without taking a vote. From there, you’re free to cheerlead, criticize, even call for a vote that isn’t going to happen, with almost no constraints.

Obviously this doesn’t describe every member of Congress.

But it explains why Congressional leaders weren’t itching for a vote, and why most members are totally fine with it.