What Do I Own?
Some investors have become concerned because they own securities that are AMBAC insured and Fitch recently downgraded the insurer to AA from AAA. We are not particularly concerned about munis that are strong credits on their own. However, there may be instances when an investor should be concerned.
The example below is for Arizona Public Service Company and is in a weekly Auction Rate mode.
It is important for the investor to understand what this security is in order to determine if it is a suitable investment for him/her. A weekly Auction Rate security has a rate that resets weekly. This rate is determined by an “auction” process. The stated maturity is shown to be 6/1/2034. This security is not deemed to be Money Market Fund eligible because a money fund can normally only invest in maturities out to a little over 1 year. It is possible, but highly unlikely, in the event of a failed auction that the investor would end up owning a security with a maturity in 2034, instead of a money market alternative. The underlying credit quality of APS is BBB-. This is shown in the Bloomberg screen shot below. While it is normally unlikely for an auction to fail, the current stress on the guarantors (in this case AMBAC) and the weak underlying credit quality of APS increase the possibility of this unlikely event occurring. 
We have avoided these securities and invest in Variable Rate Demand Notes instead. These securities are money market eligible because the liquidity to put them back to the dealer on 7 days notice is guaranteed.
Conclusion
We would caution investors to be aware of the risk of a failed auction on a weak underlying security that is guaranteed by an insurance company that cannot maintain their AAA rating.
