Sorry, but the idea that a failure to raise the debt ceiling "is most certainly going to happen" is laughable.

It might happen. It's highly unlikely, but not impossible.

If you're so certain, you should be shorting the whole market and laughing your way to the bank.

EDIT: Not to get too partisan, but the justification for not negotiating on the debt ceiling is to put a stop to the use of the debt ceiling as a form of political hostage taking.

To let this sort of thing go on gives Congress a de facto veto power over the executive branch that was never laid out in the constitution. Once you let Congress know that a majority (in a single chamber!) can get whatever they want simply by threatening to tank the whole economy, there's no going back.

That's why it's the rational policy to refuse to negotiate when a single house of a single branch of Congress starts threatening that sort of thing.