In 2012, Republicans ran against the massive cuts to defense that might occur in early 2013 under the congressionally mandated budget sequester. At an Oct. 23 presidential debate, President Obama responded that his opponent, Mitt Romney, was blowing the risk out of proportion: The cuts, he said, "will not happen."

Well, those cuts are now scheduled to take effect on March 1 - and, by the look of things, they will. The GOP has changed its tune; the Republican majority in the House seems content to let them happen.

Meanwhile, Obama, whose defense secretary has warned in the direst terms against imposing the cuts - hardly mentions the subject.

How did we get here?

The authors of sequestration, which was supposed to scare Congress into agreement on an alternative, did not anticipate the GOP's postelection maneuvering. The party is abandoning its unpopular threat to block a debt-ceiling increase - and using the threat of the sequester instead.

The goal, apparently, is still more spending cuts without any tax increases, a deal Obama properly refuses and which is less sensible for the country than is a combination of entitlement cuts and higher revenue through closing tax loopholes, which Obama might accept.

So much for the erstwhile GOP concern about gutting national security. And who cares if the sequester's cuts leave entitlements and other Democratic pet causes, such as Pell grants, unscathed?

Obama is hardly blameless. He's the commander in chief, yet in signing off on sequestration as a "forcing mechanism," he embraced a political calculation that implied national defense was more of a Republican worry than a Democratic one.

The Pentagon was already planning to trim a manageable $450 billion from its spending plans over the next decade. If sequestration happens, and continues over a decade, that figure would more than double.

As a result, the United States could have to terminate major weapons programs and would be left with the smallest ground force since prior to Pearl Harbor, according to estimates by Defense Secretary Leon Panetta.

The sequester would force the Pentagon to reduce its planned spending by 16.3 percent between now and Sept. 30, and to do so in an undifferentiated, across-the-board manner. The resulting furloughs, training reductions and procurement hassles would sow disorder and diminish readiness - while more selective cuts that might improve long-term efficiency would be bypassed.

Jobs and economic growth are not reasons to spend more than one dime than is absolutely necessary to prepare for war. But, as the most recent negative gross domestic product report shows, slowing defense production is already hurting the broader economy.

Given the uncertain global security environment, we are more skeptical than others of the need to downsize defense. But even those who disagree should recognize that sequestration is no way to go about it.

It's become a cliche of sorts to predict that partisan gridlock will undermine national security. If sequestration goes forward unchanged, that prediction will come true.