To say it with Heretic Monkey's words: Please yes, implement that because changing user names of candidates during elections can be confusing.
Voters rely on the name to identify people and they may check in at various times during the election and if then the names of the candidates change that could lead to situations where people cannot find anymore a candidate they wanted to vote for or just get confused about the identity of the candidate. I think this is a real possibility while I don't really see any big disadvantages of not being able to change the user name for a few days.
Make it a rule, write it down when announcing new elections and rollback manually if needed.