Don't believe Moore has a "slim lead". This is just an example of the phenomenon of conservatives either refusing to be polled, or intentionally giving misleading responses. It was rampant in the last presidential election, in which up until the election day itself Clinton was shown comfortably winning. And it's going on here. 

Conservatives do not trust polls or pollsters. Seldom does a subject know whether a poll is non-partisan or commissioned by a campaign. Nor do subjects know what is done with data gathered on them. There could easily be a database - by name - built on respondees to polls. Who knows what access there might be to such information and what use might be made. In this highly charged partisan atmosphere, it's easy to see why someone might not want the media to know who supported Moore?

So you'd be wise to assume that Moore's support is some 5-7% higher than polled.