>>Failing to do its duty would be a repudiation. <<
Saying that doesn’t make it true.
In fact, failing to do its duty would be a default. The difference is that the holders of the debt would still have a claim on the U.S. Government. Constitutionally, we would be required to pay it...someday. The debt would not be repudiated, i.e, our obligation to pay it would not disappear.
I’ve said before that one way to get the Left off of this tack is to simply have the House pass a formal resolution stating that any debt Geitner and Obama issue on their own WILL be repudiated at the first opportunity. And add to the resolution that it will instead be the personal responsibility of the officials who signed off on the debt. That should put a complete stop to this nonsense.
By the way, we have defaulted temporarily on our debt in the fairly recent past, I believe...the 1970’s or so. That apparently didn’t raise a constitutional question at the time. The only reason we’re even talking about the 14th Amendment is because the Left is getting desperate about this debt ceiling business, knowing the House has them in a headlock and they’re finally going down for the count.
I certainly don't believe that. What would stop Congress from "defaulting" on whatever particular debt they chose for as long as they wished? You do agree, don't you, that Congress was being limited by the fourth clause? Why bother?