Underwhelming majority
You know that Texas election last week where they approved a consitutional amendment to ban same-sex marriage?
Well, 76% of voters were in favor of the amdendment. And how many voters were there? 1,718,513. That's 18% of registered voters. Presumably the other 82% were content with the status quo.
Here's an idea - require constitutional amendments to be passed by a majority of registered voters. Sounds like an idea for a constitutional amendment.