(CNN) -- Why would a gay politician vote against gay rights?

That describes the voting record of California state Sen. Roy Ashburn, who came out Monday in an interview with a radio talk show.

"I am gay ... those are the words that have been so difficult for me for so long," Ashburn, a Republican, told KERN radio in Bakersfield, California.

The revelation from the 55-year-old father of four came after he was arrested last week, accused of driving a state-owned vehicle under the influence of alcohol. He had left a gay bar in Sacramento.

"I've always believed that I could keep my personal life personal and my public life public, but through my own actions, I have made my personal life public, and I owe an explanation to my own constituents," he said.

Ashburn has largely opposed gay rights legislation, according to votesmart.org., a nonpartisan, nonprofit political research library.

Last year, he voted against a bill to recognize out-of-state, same-sex marriages and against a bill proclaiming May 22 as "Harvey Milk Day," named after the first openly gay man elected to public office in California.

Equality California, a group that works for gay rights, said on its Web site that Ashburn "has consistently received a zero percent" on its legislative scorecards since 2004, with the exception of 2007, when he scored 10 percent.

But Ashburn's votes did not surprise Wayne Besen, founder of truthwinsout.org, which he described as a nonprofit organization that defends the gay, lesbian, bisexual and transgender community against anti-gay misinformation, counters the "ex-gay" industry and educates America about the lives of LGBT people.

"It's a perfect mask for someone who's trying to stay in the closet," said Besen in a telephone interview. "They hope that people will think that they're heterosexual. It's quite common; we've seen it over and over again. ... They're already living a lie and this takes it to a new level."

He added, "They're willing to harm themselves to protect an image of who they're not. It shows how extreme and harmful that homophobia is. The closet will force people to make decisions that will harm their own lives."

But Ashburn said he had no plans to change his votes on such matters. "My votes reflect the wishes of the people in my district, and I have always felt that my faith and allegiance was to the people there in the district, my constituents," he reasoned.

Besen was unimpressed by Ashburn's argument.

"We live in a republic, and we elect people to vote based on their conscience and what they know to be true. We could just simply have a machine do the voting instead if we relied on what the constituents wanted.

"He shouldn't be representing constituencies that are at odds with his life. He should be convincing them and arguing about what's wrong with their life."

Ashburn has announced he is not running for any public office when his term ends at the end of the year.

But one of his colleagues expressed hope that Ashburn's candor would lead him to a different view on any gay rights legislation that may yet arise.

"It's an opportunity for him to lead his caucus, to bring a new perspective to his caucus, to help them open their eyes a little bit," openly gay state Sen. Mark Leno, a Democrat, told CNN affiliate KCRA-TV.