As I watched Mitt Romney tie himself into a constitutional knot as he argued that religion should provide a guide for public policy but not be used to choose a president, it made me suspect that all the candidates in the race  Republican and Democratic  must believe that I lack some essential virtue.

I’m an atheist. When people trot out the well-worn John Adams quote, “Our Constitution was made only for a moral and religious people,” I can’t help feeling squeezed out of the polity. Mr. Romney was trying to sound ecumenical. But speeches like his confirm the impossibility for an atheist to be elected to national office in this country. Any atheist with political ambitions would have to drop the atheism first.

Atheists have solid reasons not to believe. We don’t need a divine being to explain the natural world, and don’t know why we should trust claims about humankind’s divine origins because they are in religious texts. Give “2001: A Space Odyssey” a thousand years and who knows what might happen.

Yet believing for tactical reasons has a long intellectual pedigree.

It is a variation of Pascal’s wager  one of the most famous arguments in the philosophy of religion. Articulated by the 17th-century French philosopher and gambler Blaise Pascal, it posits that rational people should believe in God even if it is impossible to prove whether He exists, simply because it is a better bet.