Turns out Harry Reid may go down in history as one of the most influential leaders the Senate has ever known—but not in a positive sense. Reid could well be remembered as the Majority Leader who did the most to make the Senate irrelevant.

Like the Tidal Basin between the Potomac River and the Washington Channel, the Senate’s power and influence has its ebbs and flows. But when the upper chamber’s influence drains out this year, it may be a long time before it returns.

Yes, Washington has been buzzing about Senator Reid’s decision to push the “nuclear option” button over presidential appointments. But the more historically significant move may be a nonaction: the Nevadan may stand idly by and allow the National Defense Authorization Act (NDAA) to die in the Senate, something that hasn’t happened in over five decades.

Congress exercises its Constitutional responsibility to “provide for the common defense” by passing key pieces of legislation: the annual defense appropriations bill, which funds defense program accounts, and the NDAA, which sets forth the policies that guide how that money is spent. The NDAA also provides direction and guidance on a host of Pentagon activities.

Congress has not passed a budget in years. The NDAA is all that is left. Now it looks like Sen. Reid is willing to let the NDAA die on his watch.

Passage of the NDAA is seldom easy. This year, the proposed Senate bill contains a number of controversial provisions, including changing the military justice system and the rules authorizing military force to go after terrorists.

But controversy is nothing new in NDAA debates. The 2012 NDAA, for example, drew fire for provisions which explicitly affirmed authorizing the indefinite military detention of unlawful combatants. Throughout the years, Congress has never found problems so big that it was willing to kill the bill over them.

Indeed, Congress has always prided itself on being able to rise above partisan politics in order to pass NDAAs. Hence, lawmakers have often titled the bill to honor their own. The 2007 NDAA, for example, was named for former Senator and Navy Secretary John Warner. The 2011 bill was named for the late, great Ike Skelton, the lion of the House Armed Services Committee.

Ostensibly, what is killing this year’s bill is a bitter, partisan disagreement over amendment procedures. And certainly there is a cloakroom war to blame the likely failure to find compromise on the other guy’s party.

Democrats lay it at the GOP’s doorstep, saying the problem stems from an internecine split between the “establishment” wing, which wants to cut a deal with the majority leader, and the “Tea Party” faction, which wants to push for votes on right-wing pet positions.

Yet if the problem is a split in Republican ranks, the majority Democrats would have no difficulty pushing through an NDAA. In fact, division reigns on Reid’s side of the aisle, too. Sen. Carl Levin, chairman of the Armed Services Committee, has no desire to go down in history as the first head of the defense committee who couldn’t get his bill to the president’s desk. Meanwhile, the party’s ultraprogressives won’t vote for any bill that doesn’t have a hike to the minimum wage tacked to it.

But these controversies are par for the course when it comes to passing an NDAA. And they are not what’s threatening to kill the bill.

The real culprit here is Sen. Reid, who seems more intent on running interference for the administration than legislating the people’s business. The calculation here is that, while an NDAA is critical for managing defense, there is nothing in it for the White House. Indeed, debate on the bill risks airing far too many issues that the Oval Office would rather not have brought up—from its debatable deal with Iran to its mismanagement of the battle against Al Qaeda. The White House simply has no interest in having its dirty foreign- and defense-policy laundry aired out on the Senate floor.

Moreover, President Obama doubtless would welcome being freed of the restraints imposed by any NDAA. The frequency and relish with which he has exercised executive authority have already led some to label his “The Imperial Presidency.” The proposed NDAA would impose numerous checks on executive power. It would, for example, continue to bar the transfer of detainees from Guantanamo Bay to the U.S. homeland and impose oversight on how the White House uses drones to go after al Qaeda. If the bill dies, all those checks on the Oval Office would disappear. All the more reason for Sen. Reid to turn the Senate into Obama’s House of Lords.

Meanwhile, there is not much the real House can do. The Speaker of the House has told Sen. Reid that he won’t keep people hanging around to sign off on a Senate bill that may never come. And looking at the dwindling number of legislative days left—both chambers will remain in town only through the end of this week—getting a deal looks increasingly like mission impossible.

The Senate, however, may have one last chance to save itself from the Majority Leader. Within a week, the House plans to pass the "pre-conference" version of the bill and send it over to Senate for an up or down vote. This option offers senators the opportunity to sidestep the debate over amendments and pass the bill.

What happens if the Senate fails to act before recess? After the holidays, Congress will bump right up against the imperative of passing another continuing resolution to keep government paychecks coming. They most likely will tack “must pass” parts of the NDAA onto the continuing resolution and be done with it.

That might be enough to keep the Pentagon going—but a terrible precedent will have been set.

It used to be said that politics stop at the waters’ edge. Failure to pass the NDAA would mean that the Senate Majority Leader is content to let politics wash over defense.

Providing for the common defense is a Constitutional duty—indeed, it is the primary justification for the existence of the federal government. No head of the Senate and no head of state should regard defense as just something else the government does—no more important than Head Start or naming hometown post offices.

James Jay Carafano is vice president of defense and foreign policy studies at The Heritage Foundation.