They did not even poll on the issue. They asked generically “would you be in favor of a background check if it would stop criminals and the mentally ill from buying a gun?” Hard to see how they ever got 10% to answer “no” to that.
About 10% of us are so conditioned to media driven pollsters that we won't give them the answer they want to hear no matter what. That's actually encouraging. Only 5% of Americans were initially supportive of the American Revolution.
Meanwhile gun sales went through the roof!