Compare Moore to the Nancy Pelosis and Harry Reeds of the party and he comes off as downright conservative. Moore makes sures that he votes with the Republicans on enough isses that he can seem moderate. He's with the party on the big ones, though.
I don't grade on the Lieberman scale. He's quite liberal by any stretch, and is no moderate. I saw Ron Gunzberger label him a "Conservative", with a straight face. It shows how disingenuous the left is. I don't know exactly what he votes with the GOP on when he scores that low, but it ain't much.