"but try to get elected after people find out you'd be affirming instead."

I'd have thought that quoting from the Sermon on the Mount (Matthew 5) would shut the critics up pretty sharpish:

...it was said in old times, "Do not take false oaths, but give effect to your oaths to the Lord". But I say to you, take no oaths at all - not by the heaven, because it is the seat of God, or by the earth, because it is the resting-place for his foot, or by Jerusalem, because it is the town of the great King. You may not take an oath by your head, because you are not able to make one hair white or black. But let your words be simply, Yes or No: and whatever is more than these is of the Evil One.

If it's ghood enough for Jesus, it ought to be good enough for those self-styled Christians...