Suppose that the Republicans are actually willing to destroy the U.S. credit rating for the foreseeable future, and to plunge the U.S. and world economies into a severe depression, unless they get their way on various issues - these being, of course, issues that they either did not even dare raise in the 2012 election, or else raised but lost on.
Anyway, suppose that they do this - despite their continuing unwillingness to name the spending and entitlements cuts that they allegedly seek - and that the Obama Administration is at least considering not folding again. (What may happen is that the Republicans will decide to destroy the U.S. economy and credit rating unless OBAMA identifies the spending and entitlements cuts that they want, whereupon they will center the 2014 Congressional campaign on denouncing him for those cuts.)
What can the Administration unilaterally do, in order to prevent the global economic catastrophe that the Republicans are threatening to impose? There are already two legal theories out there: the 14th Amendment option, invoking presidential power to prevent questioning of the federal debt, and the "platinum coin" option, exploiting an apparent loophole within legal restrictions on the federal government's legal authority to pay bills by printing money.
I believe that these two options are plenty good enough under the circumstances, but the Obama Administration keeps saying that its lawyers don't buy them. One hopes that the Administration will rethink this if necessary, but let me just throw out an alternative constitutional argument. I do this tentatively or as a trial balloon since I am not a constitutional lawyer.
This is to exercise otherwise unconstitutional (by hypothesis) presidential emergency powers to prevent a national disaster. As Abraham Lincoln famously said, the Constitution is not a suicide pact. Now, he faced a much worse emergency, in the form of armed insurrection against the U.S. government, rather than a debt default. But on the other hand he was claiming the authority to exercise far more dangerous powers - suspending habeas corpus, which is a core constitutional liberty.
If President Obama asserted that the threat of default, loss of our credit rating, and catastrophic economic consequences empowered him to authorize further debt issuance, he would on the one hand be expanding the definition of "emergency" a bit, in a potentially dangerous way. But on the other hand he would be asserting it in favor of a very innocuous departure from federal law (under the assumption, which I consider false, that he does not have the power to act under the Fourteenth Amendment or via the platinum coin trick). All he would be doing is spending money that Congress authorized and indeed instructed him to spend, instead of allowing a disastrous federal default.
Constitutional law is shot through with "balancing" approaches of one kind and another. Can one argue for interpreting presidential emergency powers this way? The idea would be that this is a big enough national emergency to permit the unilateral exercise of presidential power to do something that is both innocuous (i.e., simply following spending laws on the books) and desperately necessary to our country's wellbeing, even though it isn't a big enough national emergency to authorize his making a bigger (i.e., actual) power grab.