SCOTUS isn’t evading anything. In fact, they’ve agreed to hear two “gay marriage” cases in March. “Gay marriage” is about as controversial as it gets.
They already have three built in votes!
the courts have consistently avoided the constitutional eligibility for office issue, for starters
If it's not a constitutional issue, that's exactly what they should do - evade and avoid it because it's a states' issue. The only time SCOTUS should grant certiorari on a non-Constitutional issue is to overturn a lower federal court ruling and remand to the state court.
Gay marriage is not a Constitutional issue, it's a states' issue.