The origin of homosexuality has become something of a political litmus test for presidential candidates, almost akin to their stance on abortion. Candidates are now expected to explain whether or not they believe homosexuality is a hard-wired predisposition. It’s an important distinction, and how candidates broach the issue can really matter. Just ask Ken Buck, who drew criticism when he compared same-sex attraction to alcoholism on NBC’s Meet the Press in October 2010 during his unsuccessful Senate run in Colorado.

Since leaping into the GOP presidential race, Texas Gov. Rick Perry hasn’t been asked if he thinks gays are born or made. But in a little-noticed passage in his first book, “On My Honor,” a encomium on the Boy Scouts published in 2008, Perry also drew a parallel between homosexuality and alcoholism. “Even if an alcoholic is powerless over alcohol once it enters his body, he still makes a choice to drink,” he wrote. “And, even if someone is attracted to a person of the same sex, he or she still makes a choice to engage in sexual activity with someone of the same gender.”

In “On My Honor,” Perry also punted on the exact origins of homosexuality. He wrote that he is “no expert on the ‘nature versus nurture’ debate,” but that gays should simply choose abstinence. Perry’s campaign did not respond to a request for comment on whether he maintains this view.

President Obama has said repeatedly that people are born gay. Perry’s leading GOP rival, Mitt Romney, has remained coy about whether he thinks gays are born or made, recently saying that he is “in favor of gay rights,” but not the right to marry. Rep. Michelle Bachmann called homosexuality a “sexual dysfunction” as recently as 2004. “It is a very sad life,” she said of homosexuality. “Its part of Satan to say that this is gay. It is anything but gay.”

All of the GOP candidates, however, risk drifting away from the mainstream when it comes to civil rights for gays, a potential liability in the general election. A poll released late last month by the Human Rights Campaign, a gay rights advocacy group, found that a majority of Americans now support marriage for same-sex couples, three quarters of men say they could be friends with a gay man and nearly 60% of Americans would not mind if their grand child were gay.