Two fields, two jobs
Lead source is the answer to 'broadly, how do these people find us'. It should be a short, stable, mutually exclusive list that a person can pick from confidently under time pressure: website, phone, referral, repeat customer, paid social, paid search, home show, door knock.
Campaign attribution is the answer to 'which line item on the ad invoice produced this'. It is machine-written, not typed: campaign name or identifier, ad set, ad, and the parameters that came with the click. Humans should never have to maintain it.
Why the two fields collapse into one
The collapse always starts reasonably. Somebody wants to know which of the two spring campaigns is working, so they add 'Spring Roof Promo' to the source dropdown. Six months later the list has forty entries, half are stale, two mean the same thing with different spelling, and nobody can produce a clean channel report anymore.
Once campaign names live inside the source field, the channel-level view is gone permanently, because you cannot mechanically fold forty free-text campaign strings back into six channels without a mapping nobody wrote down.
What each field should be allowed to contain
- Source — a fixed enumerated list, changed deliberately and rarely, safe for a person to set by hand.
- Campaign attribution — machine-captured campaign, ad set, ad, and parameters; never hand-typed, never edited to make a report look better.
- Manual tag — a deliberate, auditable human override for cases the machine cannot see, stored as an override rather than overwriting the captured record.
- Notes — the anecdote ('saw the truck at the Kellers'), which belongs on the timeline, not in a reporting field.
Reporting with both
Channel-level reporting is the strategic view: it tells you whether paid search deserves more of next quarter than referral programmes. It is stable across years because the categories are stable.
Campaign-level reporting is the tactical view: it tells you which of this month's four ad sets is producing appointments that hold. It is volatile by design and only exists for the traffic that carried the detail. Keeping the two reports separate stops a tactical decision from being mistaken for a strategic one.