There are some Americans -- presumed usually to be evangelical Christians -- for whom voting for a Mormon for president of the United States is difficult, if not impossible. While I will try to show these voters why that decision is wrong on religious as well as moral grounds, it is important for the rest of us to understand their opposition.

Most traditional Christians regard Mormonism not merely as not Christian, but as a falsification of it. It does not matter to the vast majority of evangelicals if a candidate is a Christian. Most are quite prepared to vote for a non-Christian -- a Jew, for example. And they are certainly prepared to vote for Christians with whom they differ theologically -- whether non-evangelical Protestants or Roman Catholics.

But they do not regard Mormons as fellow Christians with whom they differ theologically; they regard them as having a theology so different from mainstream Christianity that they are no longer Christian. It is quite possible, even likely, that if Mormons simply announced they were not Christian, but a new religion, even one based on belief in Jesus as the Messiah and Son of God, evangelicals would have fewer objections to voting for a Mormon with whom they shared social values. Rightly or wrongly, many evangelicals resent Mormons calling themselves Christian.

It is analogous to the resentment among Jews of "Jews for Jesus." What Jews resent is not that a Jew who adopts Christian beliefs has become a Christian -- most Jews recognize that in a free society people convert to and from all religions. What many Jews resent is that "Jews for Jesus" call themselves Jews and not Christians after leaving Judaism (even while continuing to identify ethnically as Jews) and embracing Christianity. So, too, it is that Mormons call themselves Christians while embracing a different belief system that rankles so many traditional Christians.

It is not for this Jew to define a Christian. I only explain evangelical Christian opposition to Mormons calling themselves Christians to make the point that even as I understand their opposition to Mormons calling themselves Christian, I equally oppose voting for anyone based on his theology. Evangelicals have the right to proclaim Mormons as non-Christians, but they hurt themselves and their country if they measure a candidate's theology. They should concern themselves with a man's theology only when choosing a religious leader. When choosing a political leader, theology should not count.

The reason is -- and I have come to this conclusion after a lifetime of interaction with people of almost all faiths and writing about and studying religion -- theology does not appear to have much impact on people's values. Liberal Christians and Jews share virtually no theological beliefs yet think alike about virtually every important social value. So, too, conservative Christians and conservative Jews share virtually no theological beliefs, yet they think alike about virtually every important social value.

Meanwhile liberal and conservative Protestants are in agreement on theological matters -- both believe in the Trinity, in the Messiahship of Jesus, on Jesus being the Son of God, on salvation through faith rather than through works, and more -- yet they differ about virtually every social value. Obviously, shared theology doesn't create shared moral or social values.

Or take Judeo-Christian values. I have written 24 columns explicating the meaning of Judeo-Christian values, yet never once used the term "Judeo-Christian theology" because there isn't a Judeo-Christian theology. Judaism and Christianity differ on most of the major beliefs of Christianity -- the Trinity, the place of Jesus, whether the Messiah has come, the nature of salvation, and more. But they share almost every important social and moral value. Once again, the relationship between shared theology and shared values is next to nil.

Therefore the theological beliefs of a public figure should matter only when one is choosing a theological leader, never a political leader -- unless those beliefs form the basis of social and moral values that one abhors. It is very important to know the theological beliefs of one's clergyman or the head of one's seminary, but as far as the head of one's country is concerned, only his moral and social values matter. I would much sooner vote for an agnostic whose values I shared than for a believing Christian or Jew whose values I did not share.

None of this is an endorsement of Mitt Romney's candidacy or of his values. It is an endorsement of the irrelevance of his theological beliefs.