Correct me if I'm wrong, but I don't think he resigned his senate seat until he won the presidency. I sure wish he was still a carping liberal senator.
Correct me if I'm wrong but running for president is a full time job and so is being a Senator (or Governor).
Correct me if I'm wrong again, but it seems to me that the politician who resigns their job to run for president instead of staying on as senator(or governor) is the politician who is doing the correct(ethical) thing.