Can the president save Congress from itself?

With no fiscal 2014 budget in sight, the debt ceiling looms — the Treasury claims it will run out of money to pay bills as early as Oct. 17.
The prospect of national default has revived the 2011 debate — from the last time this program ran — over the 14th amendment. Led by Prof.  Sean Wilentz’s full-throated endorsement (but also see here and here), proponents of the so-called “constitutional” solution to the crisis argue that President Obama should simply invoke the fourth section of that amendment — which states that “the validity of the public debt of the United States, authorized by law… shall not be questioned. …” — and set aside the debt ceiling statute on his own authority.
The amendment itself, of course, was passed in the aftermath of the Civil War, with this section included out of fear that some coalition of Southern politicians back in federal office and northern politicians pushing inflationary paper currency would repudiate or at least devalue the debt run up by the Union. (The amendment also sets aside any claims made by former slaveholders seeking compensation for losing their property via emancipation.) In its 5-4 decision in the 1935 case Perry v U.S., the Supreme Court rejected the notion — in dicta, at least; at least one concurring justice thought the decision went too far afield — that “when, with adequate authority, the government borrows money and pledges the credit of the United States, it is free to ignore that pledge and alter the terms of its obligations in case a later Congress finds their fulfillment inconvenient.”
So far, so good; but it is worth noting, for instance, that the amendment applies to debt “authorized by law,” which bonds issued above the debt ceiling would not be. The court’s statement that “the Congress has not been vested with authority to alter or destroy those obligations” also refers to obligations already issued. (So things quickly get tricky, in that the current debt ceiling is preventing paying back older borrowings: The old debt, authorized by law, can only be paid off by new debt, not authorized by law …)
Along those lines, it is worth mentioning too that the 14th amendment has five sections, not four: The fifth states that “The Congress shall have power to enforce, by appropriate legislation, the provisions of this article.” The debt limit statute is itself “appropriate [if hugely unhelpful] legislation,” entirely consistent with Article I’s assignment of the power of the purse to Congress. Given the shift in the early-ish 20th century from legislative approval of individual debt issues to broader delegation of that authority to executive branch actors, a check on the scope of that delegation is rational enough.
The White House, thus far, has called the 14th amendment approach a “unicorn theory” of governance; Harvard Law’s Larry Tribe has argued strenuously against it as well, noting that “The Constitution grants only Congress — not the president — the power ‘to borrow money on the credit of the United States.’ ”
Still, is it really true, as Prof. Tribe recently contended, that “we have no metric for comparative lawlessness”?  Murder is worse than shoplifting, surely; perhaps default is worse than the illegal issuance of new debt. Perhaps the passage of a budget de facto requiring the issuance of debt that exceeds the limit is another, competing, piece of “appropriate legislation.” Perhaps the administration could prioritize bill payments despite the lack of clear legal authorization for doing so.
This is the tack taken by scholars such as Henry Aaron of the Brookings Institution. Aaron recently argued that, if House push comes to Senate shove, Obama should ignore the law establishing a debt limit and continue to pay the United States’ bills as they come due. This would be illegal. But, he says, it is also illegal to set aside payments and debts legally obligated by past congressional action. Thus unilaterally setting aside the debt ceiling would be the least worst place to go.
I would stress that this focus on competing illegalities distinguishes it from the “constitutional” option above. The 14th amendment approach would have the president claim a specific clause of the Constitution gives him authority to act. Aaron’s approach — see too Prof. Eric Posner’s recent assessment of the situation — does not.
As a result, it is both more honest but also more broadly dangerous for the ratcheting effect its use might have on presidential power. For it rests on the power of prerogative, residing in the vagaries of the vesting clause of Article II. “The executive power,” the Constitution says, “shall be vested in a President… ,” but what that executive power actually is is never defined.
Prerogative itself is defined by  the political philosopher John Locke in his 1690 Second Treatise on Government as the “power to act according to discretion, for the publick good, without the prescription of the law, and sometimes even against it …” “It is fit,” Locke went on to say, “that the laws themselves should in some cases give way to the executive power. … : for since many accidents may happen, wherein a strict and rigid observation of the laws may do harm…. therefore there is a latitude left to the executive power, to do many things of choice which the laws do not prescribe. … This power, whilst employed for the benefit of the community, and suitably to the trust and ends of the government, is undoubted prerogative, and never is questioned.”
A number of political scientists have examined the facts and justifications for presidential prerogative. Benjamin Kleinerman, in his book The Discretionary President, tries to thread the needle by arguing that prerogative, if not legal, is nonetheless constitutional — and, indeed, essential in times of emergency. Afterwards, presidents must make their case that they have,  indeed, acted for the “publick good.”  Michael Genovese, by contrast, in Presidential Prerogative, argues that “no … Lockean prerogative found its way into the Constitution, and virtually all evidence from the founding period suggests that the inventors of the presidency rejected prerogative powers.”
So it is hardly true that prerogative “never is questioned.” Indeed, it needs to be, given the potential precedent its use would establish (which liberals urging presidential action now might like less in different hands.)
But at present it seems quite possible the White House will come to believe in unicorns, even if not necessarily those spawned by the 14th amendment. After all, most of inter-branch history — and certainly the meaning of “the executive power” — has been defined in practice rather than in theory. Thus the questions shift quickly from the legal to the political. Would and could courts enforce the law? (And which law?)  Would impeachment ensue instead?  And, most crucially, do Congress’s (still only potential) failings in this area constitute a national emergency that necessitates — or at least provides cover for — presidential action in violation of the law, in Lincolnesque fashion? (Is the debt limit crisis the equivalent of the Civil War?)  It is up to Congress to prevent these questions from becoming more timely.