Extending the debt limit is necessary to pay the bills the country already owes. As Republican Sen. Chuck Grassley argued before there was a Democratic president, “Raising the debt limit is necessary to preserve the full faith and credit of the U.S. Government. We cannot as a Congress pass spending bills and tax bills and then refuse to pay our bills. Refusing to raise the debt limit is like refusing to pay your credit card bill — after you’ve used your credit card.”

Now, of course, Republicans want to rewrite the rules and not pay our bills. There’s a credible debate underway as to whether the GOP even has a choice in the matter.

The 14th Amendment to the Constitution seems to prevent the United States from refusing to pay its bills. The language reads, “The validity of the public debt of the United States, authorized by law … shall not be questioned.” This constitutional provision, according to some legal scholars, offers President Obama a way out if congressional Republican decide they’d rather shoot the hostage: he can pursue the “14th Amendment Option” and simply pay our obligations anyway, debt ceiling be damned.

The subject came up briefly during yesterday’s White House Twitter Town Hall, with President Obama saying, “I don’t think we should even get to the constitutional issue. Congress has a responsibility to make sure we pay our bills.”

Left unsaid is what the president is prepared to do if Congress ignores its responsibility and refuses to pay our bills.

Constitutional experts can speak to this dispute with far more authority than I can, but it’s worth noting that the mere possibility is starting to cause a minor freak-out in Republican circles.

Later today, Sen. Lindsey Graham (R., S.C.) and Sen. John Cornyn (R., Texas) will introduce a ‘sense of the Senate’ resolution that says the president does not have the authority to sidestep the debt ceiling, which is set to expire in August.

“I strongly disagree with those who suggest the president has the unilateral authority to put the American people in even great levels of debt,” Graham says in a statement. “Every time the debt ceiling has been raised it has been through an act of collaboration between the president and Congress. That is not only the right policy decision to make, but the correct political decision as well. We have a president, not a king. Our resolution puts the Senate on record that any debt-limit increase, today or in the future, should be passed by the Congress and signed by the President.”

Graham isn’t lying when he says, in the past, debt-ceiling increases have always been “an act of collaboration between the president and Congress.” What he neglected to mention, though, is that we’ve never had a party prepared to pursue default, on purpose, and jeopardize the full faith and credit of the United States before now.

It is, in other words, a new ballgame, which may require a new solution to prevent a deliberate, avoidable catastrophe.

What’s more, note that Senate Republicans aren’t the only ones feeling antsy — a House Republican this week raised the specter of presidential impeachment if Obama goes down this road.

In case this isn’t already obvious, it’s worth acknowledging why the GOP is panicking, and it has nothing to do with constitutional principles or separation of powers. The issue is one of leverage — if the “14th Amendment Option” (or, “Constitutional Option”) is legitimate, the Republican hostage strategy starts to crumble. There would be a built-in safety valve in the event talks collapse and the GOP decides to go through with the party’s threats.

In other words, right now, Republican leaders are saying, “Meet our demands or we’ll shoot the hostage.” If this constitutional work-around is a viable alternative, the president can say, “Never mind, I’ve found a way to save the hostage without you.”

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.