PMax will spend your budget wherever it is cheapest to convert — which is usually branded search. Here is the structure we use to force genuine incrementality.
Performance Max is not a campaign type so much as a budget allocator. Left alone, it will find the cheapest conversions available to it, and for most advertisers the cheapest conversions are people who were already going to buy.
Separate branded demand first
Before you judge PMax on ROAS, exclude your brand terms with a brand exclusion list and run branded search as its own campaign. Almost every "amazing" PMax result we audit collapses by half once branded traffic is carved out.
Split by margin, not by product type
Group asset groups and listing groups by contribution margin. A 60%-margin product and a 12%-margin product should never compete for the same budget under the same ROAS target.
Feed the algorithm real value
Send back actual revenue or, for lead gen, the value of a sales-qualified lead through offline conversion imports. Optimizing to form fills teaches the system to buy form fills.
Give it enough creative
Each asset group needs genuine variety: at least five images, three videos, and headline sets that express different value propositions. If you do not supply video, Google will generate one, and it will not be good.
Read the reports that exist
Asset group performance, search themes, and the channel breakdown available through scripts give you more visibility than most advertisers use. Check them monthly, prune what underdelivers, and rotate creative on a schedule.
Done properly, PMax is a strong channel. Done by default, it is a branded-search tax with extra steps.
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