In the 1990s and up until the late 2000s, I was okay with a Democrat that wasn't in favor of marriage equality. I was convinced that this issue would eventually be resolved via the Supreme Court, and that court appointees were of much more importance than what the President thought. The only issue that would've made it through Congress in the political climate of those years was maybe the Employee Non-Discrimination Act, and Clinton has always said that he'd sign a bill if it made it to his desk.
So legislatively, I was being realistic/strategic with my vote. I don't have any data on-hand, but my suspicion is that many other LGBT voters from those years had similar thought processes. Looking at where the country was, we were playing the long game.
The year after Bill Clinton was elected, he appointed Ruth Bader Ginsburg to the Supreme Court. Ruth Bader Ginsburg - general counsel of the ACLU. Yeah! That was all I needed to know about whether he was worth my vote as far as gay issues were concerned.
Overturning sodomy laws was of utmost importance back in that era; it was 1986 when the Supreme Court had ruled sodomy laws constituional in Bowers v Hardwick. Laws deeming our private consensual acts criminal were given the stamp of approval; this horrified many of us, and I (along with many others) voted while hoping that Clinton's appointees would greatly help in removing them. No other progress on gay rights issues could be made until that first key obstacle was removed.
This voting strategy paid-off handsomely in 2003, when the Supreme Court - with help from Bill Clinton's two appointees - overturned Bowers in Lawrence v Texas. After Lawrence, marriage was the next goal. And legal success that occurred at the Supreme Court reinforced my belief that Supreme Court appointees were of utmost importance when considering a politician's LGBT rights stance.
Would I have liked Obama and Hillary and Bill to come out in favor of marriage equality sooner? Absolutely. But they ended-up in the right place, explained their thought processes, and still helped the cause along in a prudent manner, even if it had to be a bit covert because of the electoral climate. Instead of turning my fire on folks who are now in a good place, I'd rather focus my fire on folks who wouldn't hesitate to appoint judges that would restore Bowers.