100% correct - he'd lose congress immediately. While I was no fan of Mccain's irresponsible spending and lack of independence from Bush, I would carry signs all day for republican congressional candidate if Obama tried banning guns.
It's political suicide to even raise the topic.
Unfortunately Obama's detractors are at a loss for substantive critiques of the man's policies so they invent bullshit and run with it.
We'd better get used to it.
It's only a matter of time before it devolves into, oh, I don't know, some white broad going on the national liberal media and accuse Obama of raping her.