First, Washington Post is full of it. Second, strong leftist or rightists get nowhere in politics, so of course he's relatively moderate. Last, gun control IS strong by definition. So this is a loaded poll.
Stefy, not everyone know his stance on gun control, most people don't even know who he is. Many who do assume that because he is a democrat he is also anti-gun. I think the poll is just asking if we are aware of his position on the issue.
Exactly, like what Brain said. Nobody evens knows who he is. Also, most aren't aware a far left candidate would even support the idea of guns. This is good, because he can attract some gun owners to vote for him. (This is also a big reason why Al Gore lost in some states back in 2000)