I couldn't find anything in a quick search of the Canon Law of the Episcopal Church but someone may be able to.

I did find a wikipedia entry that stated that Pope John Paul II had only explicitly forbidden RC priests from holding public office in 1980. So I am going to conclude that it was allowed in the Episcopal Church. We even had a racist as shit bishop who turned traitor and served as a general in the CSA army, so surely a little political office holding would be allowed.