Is it possible to send a campaign to multiple lists?
A campaign can only be sent to one list at a time. This helps to prevent you from sending your campaign multiple times to the same subscriber, but you can always override this by duplicating your campaign and sending it to another list.
If you regularly find yourself needing to send to multiple lists, you may want to consider placing all of your contacts in a single list. You can then use segmentation to select a portion of those contacts at send time.