It is possible to duplicate existing campaigns, for instance, if you want to run a campaign again later because it converted well or any other reason.
To duplicate a campaign, first navigate to the campaign that you wish to duplicate and select the “Duplicate” item from the options menu in the upper right.
The new campaign will have all the configuration copied over from the original campaign. Now you have an opportunity to customize the things that will be different this time (notably, the start and end dates.)
Note that conversion metrics will not be copied over, since this is, conceptually, a new campaign that is a copy of the old campaign.