The step nobody fills in
Associations links forms, webpages and sequences to the campaign. Skipping it does not break generation, which is exactly why it gets skipped.
Wire the campaign to the forms, pages and sequences it depends on, so that what it produces can be traced back to it.
Step four is Associations, and its subtitle states the job: link forms, webpages and sequences to this campaign. It is the least glamorous step in the builder and the one most often clicked past, because nothing visibly fails when it is left empty. The assets still generate. The campaign still launches.
What quietly does not happen is attribution. The leads captured by a form that is not associated with this campaign are leads the campaign will not be credited with, and the campaigns report will show a campaign that produced assets and no pipeline. Weeks later somebody looks at that row and concludes the campaign did not work, when what actually happened is that nobody spent ninety seconds on step four.

Campaign UTMs appear on the Review step alongside the audience and asset counts, and generated landing page URLs carry them automatically. That is worth knowing before someone on your team builds a parallel tagging convention in a spreadsheet, which is the usual outcome when people assume tagging is their problem to solve.
Two schemes are worse than one, because traffic then splits across both and neither view is complete. If your organization has an existing UTM convention that differs, reconcile them deliberately rather than running both and hoping the reports can be added together later. They generally cannot.
The example campaign needs three associations: the "Platform evaluation guide" form (the conversion point on the landing page), the campaign landing page itself once pushed to HubSpot, and the "Post-download nurture" sequence that picks up converters. Each is searched and linked on step four in under two minutes.
Then the UTM check on the review step: the campaign's generated parameters will ride on every landing page URL. Your team's existing convention tags source and medium differently for paid social. The reconciliation decision, to adopt the campaign's parameters for everything this campaign touches, is written in the campaign description so the next person does not "fix" it back. Total time for the step that protects all attribution: under ten minutes. The cost of skipping it: a report in six weeks showing a campaign that produced 44 assets and, apparently, nothing else.
Do this in the product
You should be able to answer each of these from memory before opening it. Recalling the answer is what makes it stick; recognizing it when you read it does not.
Nothing visible at launch, which is why it gets skipped. Attribution fails later: leads from an unassociated form are not credited to the campaign, so it reports assets produced and no pipeline.
The campaign itself. They are shown on the Review step and appended automatically to generated landing page URLs, so building a second tagging scheme by hand splits the traffic across two incomplete views.
Associations links forms, webpages and sequences to the campaign. Skipping it does not break generation, which is exactly why it gets skipped.
A campaign that is not associated with the form capturing its leads will report as though it produced none of them.
Campaign UTMs appear on the Review step and are appended to generated landing page URLs. Do not hand-roll a parallel scheme.
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