I'm curious... do you have a way of looking at how many webpage hits you have from the Craigslist ad? If you're getting traffic, but no one biting, then maybe no one is interested in that particular thing.
I notice, by the way, that you don't list your ad's title. Do you have an ad specifically for "bassist," "keys," and "drums?" Just asking for musicians can make it seem like you don't yet have a band... and, frankly, the fact that you only have two members so far, and that they're both guitarists, might make me hesitate to jump into a situation where two of the normally more dominant roles in a band are already filled, and where I'm likely to be a backup to whatever their little music fest has already be decided to be.
I'm no longer from your area, but I met quite a few guys through word of mouth when I lived in the DC area, and it was normally through networking that I met people with whom I wound up playing. If you're only relying on Craigslist, I'd recommend hanging in music stores. I had Atomic Music near me (Greenbelt MD), but I'd hope that you'd have something similar near you. Shmooze. Make connections. "Hey! How's it going!" I knew a bunch of guys who knew other guys, and since I was sociable, i could just toss out, "Do you know of any decent bass players who are looking for a situation? Well, currently we're doing this, but really, I'm open to see what emerges when someone else brings their stuff to the table. I don't want to rule anything out."
Of course, if you're committed to a particular sound before you have the staff to do it, you don't need to abandon that. However, I've had better experiences with being open to what might come along than when I had hard and fast expectations.
If you don't care enough to research your own question, why should anyone else care more?
"Pay no attention to his long winded posts... (Explorer) seldomly knows what he's talking about."
"Actual knowledge and a google bookmark are very different things." Anonymous neg-repper