So maybe, as Doc Brown would say, in considering the subject of gay rights and Republicans, I'm not thinking four-dimensionally. My instinct tells me that a presidential candidate who supports gay rights cannot make it through the gauntlet laid down by social conservatives in the GOP primary. Here's why I might be wrong:
1. So if you're Sen. Rob Portman, and you're likely to be in the VP nominee mix in 2016, your support for gay rights separates you from the other potential ticketmates. If you're Marco Rubio, picking Portman would help in Chicago and potentially bring in some credibility with younger voters. By 2016, given the trajectory of the issue, it will probably break 55 to 45 against the GOP or worse.
2. Thought bubble: Marco Rubio came out on a charm offensive on immigration a few months ago and has seen no deterioration in his poll numbers. If he had instead come out with a view on gay marriage that government shouldn't be involved at all and marriages were up to churches, would the results be any different? I recall the immigration backlash against Sen. John McCain and it's true that the passions on that issue were and are no less strong than on gay marriage within the GOP base.