I was just watching Bill Maher on HBO and he was commenting on the US Senate bill on gun control that failed recently.
He was saying that 90% of Americans "support background checks."
I highly doubt this, but I live in redneck country.
Politifact.com's "Truth-o-meter" has looked at this - or at least Gabby Gifford's softer variant, which answers the question here too.
Giffords’ claim is well-founded, in part because it’s not overly specific: In four polls over the prior month, between 83 percent and 91 percent of respondents said they would favor an expansion of the current background check regime. We think any reasonable person would conclude that those percentages qualify as "overwhelming."
However, they weren't willing to give other claims similar to Bill Maher's the same green-light:
Giffords would have had more trouble finding support for her claim had she either set a numerical threshold or had she been more specific about the kind of background checks Americans are comfortable with.
For instance, when Obama spoke shortly after the amendment’s failure in the Senate, he cited 90 percent support for an expansion of background checks not once but five times in fairly brief remarks. In the survey results we found, half of the polls crossed that threshold and half did not (though those that didn’t are fairly close).
Given Maher's claim is the same as Obama's we can conclude that it is supported by some polls (e.g. Qunnipiac and CBS, but not quite supported by others (Washington Post and CNN - depending on the question).