There is an option to archive the campaign.
Select the relevant campaign and with in the pop-up window, click the icon on the top right hand corner an choose “Archive”.
By clicking archive, the campaign will disappear from your admin panel. To recover it you’ll have to contact support and provide the name of the campaign.
Please note, you’ll still be able to view and export your connections and prospect’s data.
Generally, we don't recommend to delete/archive campaigns because you never know when all of the people invited through a particular campaign will accept your invite to connect. By leaving the campaign as it is, you always have the ability to send a followup message to that targeted audience.
We recommend you turn off the 'invites' setting for that campaign and leave it on the back-burner for a while.
Try running followups with it a week or two from now if you're still interested on following up with that audience. Or, simply add a note to yourself in the heading of the campaign reminding yourself and other users not to play it.