Depending on the size and budget of your campaign, having a staff HQ may not be feasible. Statewide campaigns may include volunteers from across large states, and meeting regularly will not be an option. Wile videoconferencing is great for small groups, there is no substitute for old-fashioned conference calls for larger groups.
Totallyfreeconferencecalls.com provides reliable rooms with good audio quality to accomodate up to 500 people at a time. They also offer paid services to host larger calls. Most campaigns will not need more than the free service offers, however.
There are a number of other features that make this service attractive. A web dashboard allows you to monitor connections to the room in realtime, and to mute and unmute callers. An optional (and also free) recording service is available that records your call and makes it available for download and playback for 30 days.