When I delete a campaign, it's actually still there. I just see its status to be 'Deleted'. How can I permanently and physically delete a campaign? Or is it not doable?
You can't, nor should you even want to. Old campaigns are always good to refer to for educational purposes.
If you don't want to see that deleted campaign you can click "Show: all active or all but deleted" in the top-right corner.
Yep, you can hide it, but you can't delete it. Google uses ALL your previous campaigns as one part of figuring your QS and CPC. They never forget. lol But on the bright side, a couple good ones and you will.
Old campaigns aren't terrible to have hanging around, it's interesting to go back in time and see all your mistakes in keyword grouping which resulted in exorbitant bid prices.