Chait sizes up the politics of the 14th Amendment option:
[I]t's not even clear that the Republican leadership actually wants the enormous and destructive power it now demands. Its base may be demanding a debt ceiling showdown, out of specific opposition to Obama and general ignorance of how the debt ceiling works. But John Boehner knows full well that we can't just ignore the debt ceiling. If Obama successfully asserts the power to ignore the debt ceiling vote, then he'll allow the debt negotiations to proceed in a less fraught environment, and have defused a massive source of ongoing political instability. Cutting a deal to lift the debt ceiling may soothe the markets more in the short term, but it merely pushes the political risk further back.
The Dish 