I was able to successfully import the campaign on a contribution by importing the campaign's CiviCRM ID.
I agree that it seems odd that campaigns have an "External ID" field, but it can't be used for imports, though!
I was able to successfully import the campaign on a contribution by importing the campaign's CiviCRM ID.
I agree that it seems odd that campaigns have an "External ID" field, but it can't be used for imports, though!