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Hi! Jo from the Moz support team here. Unfortunately, you can't add more than 3 competitors per campaign. However, you do have the option to create a new campaign for the same website using another set of different competitors, if you wanted to do that. If you were looking for extra competitive link data, Open Site Explorer would give you the ability to compare up to 5 sites within the 'Compare Link Metrics' tab, here is the guide. I hope that helps! Best, Jo