I think that the (lack of) voting, close voting, editing, and tending the queues are all definitely due to a lack of active users, as both Al and phwd have pointed out. The fact that we have closed questions based on the votes 5 regular users only a handful of times has been more bothersome to me than the voting for a while, to be honest.
As phwd pointed out, we're getting less through traffic than normal because of various Google Panda changes that have happened sporadically, but compounding this problem is that the quality of what questions we do bring in has dropped dramatically as well.
We're down, but we're not out. Not yet.
We have our strengths, and we need to play to them. For example, we have an excellent repository of information in How do I recover my Google account (or Gmail) password or username? that gets a lot of hits, and we close a lot of duplicates to that question, which, at first blush, seems like a bad thing. With each of those duplicates, though, we get more and more search terms out there that attract traffic to the site. I think we need more "canonical" questions like this, in particular for Twitter and Facebook. We have a lot of "near duplicates" on those that aren't really being closed either, largely because of the nuances between the questions that could be covered by a canonical post. Google Spreadsheets has been one of the few boons for us over my tenure here, and we have a (very) small group of dedicated users that attend to these questions, but some of those questions could probably be adopted into more canonical ones as well.
A lot of that seems "pie in the sky" considering that our active users are way down, but I think the notion of "If you [re]build it, they will come" (pardon my triteness) holds here. Instead of "If you see something, say something", I think we need to adopt an approach of "If you see something, fix something", whether that's a question title that needs to be shored up or an answer that's right on the money (or at least a giant step in the right direction), but may be a bit broken in the grammar and style department. Speaking of style, I'll restrict my sloganeering to this one paragraph.
To be completely fair, there is a "posse" of dedicated users that are doing most if not all of these things already (and thank you all, you know who you are), but if a group of less active users put forth one change (edit, etc.), we'll be able to start to fix things that are hampering us from surviving and thriving.
I realize that my approach to answering this has taken me a bit off of the original theme of how to draw more voters, but I think that some of the above-mentioned changes will result in a higher quality (and hopefully quantity) of traffic, and will bring more worthy questions that will receive better answers, etc.
This is my sense of things, but it's not designed to be any sort of edict. (Please) comment, react, tell me I'm wrong. Any and all suggestions are welcome, whether you've been on the site for one day or 4 years.