You’ve been hired by the A.C.L.U. to win over Republicans on same-sex marriage. What’s the argument that you make to those who are resistant?

A few years ago, there was universal agreement in the party that marriage is between one man and one woman. It was a position that appealed to the middle of the electorate. That’s not true anymore. Politicians have an acutely honed instinct for self-preservation. Over time I am convinced this issue will be a political liability for people who are opposed to it.

You came out in support of same-sex marriage in March 2009, several months after your former boss John McCain was defeated by President Obama. Had you shared your views with him?

Yeah, absolutely. And I wasn’t the only member of the senior staff who felt that way. But he was pretty typical of someone of his generation and someone who was the nominee of the Republican Party. I suspect that the next Republican nominee will also be opposed to marriage equality. But sometime after the next election, you will ultimately see Republican nominees in favor of it.

George W. Bush was also against gay marriage. Given that he was personally very supportive of gays in his administration, were you disappointed in him for not extending rights to gay couples?

A lot of people like me who worked in Republican politics had a personal set of beliefs on issues that were at variance with the candidates that we worked for. Over time, that accommodation became more difficult to rationalize. I came to the point of view that I don’t want to work on political campaigns that have as a central pillar denying people what I think is a fundamental right.