Assuming that one has broadly diversified municipal bond holdings, the threat would not seem to come from a biblical-scale wave of defaults. (I must admit that we have no data on muni defaults during biblical times.) The bigger threat to a broadly diversified muni portfolio would seem to be the typical market cycles of run-up followed by correction followed by run-up.
Michael Holland: Among the thoughts I agree with from Vahan and Barry is that, after a huge run, the market obviously can have a correction of significance at any time.
In the month since the stock reached new, 52-week highs, the stock pulled back to retrace about 25% of its August-July run as part of a five-day correction that took shares of NLS into short-term oversold territory.