To delete a challenge, you must have admin rights. Click ‘Delete challenge’ on the far right drop down in the expanded view:

When a challenge is deleted, by default, all ideas that have been submitted to the challenge remain as standalone ideas, no longer being attached to that challenge. To delete all ideas and the challenge itself, click the ‘Yes’ button next to ‘Would you like to permanently delete all ideas posted to this challenge?’

Did this answer your question?