[amyjess]

Not necessarily. While SCOTUS legalized gay marriage after public support for it passed 50%, it wasn't until decades after SCOTUS legalized interracial marriage that public support for it passed 50%.

xkcd has an interesting graph of this: https://xkcd.com/1431/

[erispoe]

You are right. I don't think SCOTUS looks at gallup polls and decides to endorse anything that meets a 50% threshold. It's more about recognizing a change in opinion and a consensus in the making. Interracial marriage was not at 50% but firmly on the way up.