The WSJs Timiraos, in an article outlines the "loathsome" playbook in the event of a Debt-ceiling standoff. The expectations are that we don't get to that point but you never know.

Potential actions from the Fed include

Once again, it is probably not the odds on favorite for a debt ceiling plan not passing, but, if an agreement is delayed and it forces a shutdown (it is likely to be temporary), it is best to know what can be done. Regardless, however, the rating agencies would likely downgrade US debt, that could force rates higher (at least in the short term) and likely lead to increased risk in other markets including stocks.