Depends on the context and how conservative you are (in the sense of tradition for tradition, not politics or anything else). Tradition holds that you call someone at that level of elected office by their previous title. If you want to break with tradition, you can call them whatever you want. You didn’t sign any legally binding agreements that say you have to call someone a fancy title. This holds for judges, doctors, and other people that think random chance and living their life gives them a special name that you don’t get.