Quite: the oath of office is not an oath that has to be taken on a bible, but if someone who was or pretended to be religious elected to take the oath and not use their highest scripture to swear on, people would wonder in what way they wanted to break it without going to hell.

And to be elected President, one has to be religious or pretend to be, though many politicians are, of course, the "Easter and Christmas Day" kind of Christians.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.