Section IV of the 14th Amendment to the US Constitution says the validity of the debt "shall not be questioned." Yet, Congress plays politics with the debt ceiling (as put in this Atlantic article, they "point a gun at the national credit rating and scream, 'One step and I'll shoot!'"), and default has been threatened over the course of these battles (thankfully, that's done for this administration, just before another threatened default). The financial market shows evidence that investors "view the credit of banks as superior to that of the U.S. government."
What is the constitutionality of these limits and political games that do seem to cause people to question whether or not the debt will be paid?
Wasn't the point of this amendment to prevent Congress from playing politics with the debt?