lol on the play one on wikipedia comment an office under the united states is afaik any government office federal state or local i would imagine that just as it would be a breach of separation of powers for someone to be simultaneously congressman and president it would be a breach of federalism for someone to simultaneously serve in two different governments i have no idea why the seniority date isn't the actual date of oath taking but he couldn't have voted on federal legislation until he resigned as a city councilman and was sworn into congress so there was in reality no dual office holding