Several gay friends and wealthy gay donors to Senator Barack Obama have asked him over the years why, as a matter of logic and fairness, he opposes same-sex marriage even though he has condemned old miscegenation laws that would have barred his black father from marrying his white mother.
The difference, Mr. Obama has told them, is religion.
As a Christian — he is a member of the United Church of Christ — Mr. Obama believes that marriage is a sacred union, a blessing from God, and one that is intended for a man and a woman exclusively, according to these supporters and Obama campaign advisers. While he does not favor laws that ban same-sex marriage, and has said he is “open to the possibility” that his views may be “misguided,” he does not support it and is not inclined to fight for it, his advisers say.
Senator John McCain also opposes same-sex marriage, but unlike Mr. Obama’s, his position is influenced by generational and cultural experiences rather than a religious conviction, McCain advisers say.
But Mr. McCain, reflecting his strongly held views on federalism, has also broken with many Republican senators and joined Mr. Obama and most Democrats to oppose amending the United States Constitution to ban same-sex marriage, arguing that the issue should be left to the states to decide.
The candidates have very different positions, though, when it comes to the state level. Mr. Obama opposes amending state constitutions to define marriage as a heterosexual institution, describing such proposals as discriminatory. Mr. McCain, however, has been active in such efforts: On the most expensive and heated battle to ban same-sex marriage this year, a proposed constitutional amendment in California known as Proposition 8, he has endorsed the measure and sharply criticized a State Supreme Court ruling that granted same-sex couples the right to marry.
Mr. Obama has spoken out against Proposition 8, and opponents of the measure hope that a huge Democratic turnout in California on Nov. 4 — and, possibly, depressed turnout among conservatives — will help defeat it. At the same time, some Democrats say that if many socially conservative blacks and Hispanics turn out to support Mr. Obama, but oppose same-sex marriage, the amendment’s chances for passage could improve.
While same-sex marriage is not expected to play a consequential role in the elections on Tuesday — unlike in 2004, when a proposed ban in Ohio was widely seen as hurting the Democratic presidential nominee that year, Senator John Kerry — passions remain high for voters on both sides. Some gay Democrats had hoped, in particular, that Mr. Obama would extend his message of unity and tolerance to their fight on the issue.
“Barack is an intellectual guy, and I know he has been thinking through his position on gay marriage, and what is fair for all people,” said Michael Bauer, an openly gay fund-raiser for Mr. Obama and an adviser to his campaign on gay issues. “But he is just not there with us on this issue.”
Some gay allies of Mr. Obama thought, during a televised Democratic forum in Los Angeles in August 2007, that he might come out in favor of same-sex marriage, after he was asked if his position supporting civil unions but not same-sex marriage was tantamount to “separate but equal.”
“Look, when my parents got married in 1961, it would have been illegal for them to be married in a number of states in the South,” Mr. Obama said. “So, obviously, this is something that I understand intimately. It’s something that I care about.”
At that point, he veered onto legal rights, saying that — both in 1961 and today — it was more important to fight for nondiscrimination laws and employment protections than for marriage.
Mr. Obama has spoken only occasionally about his religious beliefs influencing his views on same-sex marriage, and he has indicated that he is wary of linking his religion to policy decisions.
“I’m a Christian,” Mr. Obama said on a radio program in his 2004 race for Senate. “And so, although I try not to have my religious beliefs dominate or determine my political views on this issue, I do believe that tradition, and my religious beliefs say that marriage is something sanctified between a man and a woman.”
In one of his books, “The Audacity of Hope,” however, Mr. Obama describes a conversation with a lesbian supporter who became upset when he cited his religious views to explain his opposition.
“She felt that by bringing religion into the equation, I was suggesting that she, and others like her, were somehow bad people,” he wrote. “I felt bad, and told her so in a return call. As I spoke to her, I was reminded that no matter how much Christians who oppose homosexuality may claim that they hate the sin but love the sinner, such a judgment inflicts pain on good people.”
“And I was reminded,” Mr. Obama added, “that it is my obligation, not only as an elected official in a pluralistic society but also as a Christian, to remain open to the possibility that my unwillingness to support gay marriage is misguided, just as I cannot claim infallibility in my support of abortion rights.”