Deleting a campaign is safe. Here is exactly what it does.

Once you delete a campaign, you will no longer see it. Extrovert stops fetching new posts for the people in it, and it disappears from your campaign list.

The prospects of a deleted campaign stop counting against your team's prospect limit, and the topics attached to a deleted Topic campaign stop counting against the topic limit. Stopping a campaign does not free anything, because its prospects and topics are still there. If you later add the same person again, they take a place again. See how prospect limits work.

Deleting a campaign does not erase your history with those people. If you later add the same person to another campaign, their history comes back with them. So you can safely delete a campaign you are done with and start fresh elsewhere, without losing your past activity.

Open the campaign's menu (the three-dots icon) and choose Delete campaign. You need permission to delete it, which means you are the campaign owner, or an admin or manager on the team. You can still delete campaigns after your plan has ended.

Any comments you already posted stay live on LinkedIn. Deleting the campaign only stops future activity, it does not remove what was already published.

The confirmation message mentions prospects being removed. That means they leave this campaign, not that your history with them is erased.

Deleting a signals campaign stops its tracking. The people it already found stay in Suggested prospects, and credits it spent are not returned. As long as someone still owns a signals campaign, that team member, their account or the workspace cannot be deleted. See Intent Signals: find prospects by what they do on LinkedIn.