No tariff
Buying widgets from the foreign manufacturer has a price of $100 per, and is subsequently resold by the importer on the domestic market for $130 per.
$20 tariff imposed.
Several things can happen.
foreign manufacturer pays 100% of the tariff
Importer demands the foreign manufacturer lower their price to $80, so their cost is still $100, and the product is still resold for $130.
importer pays 100% of the tariff
Foreign manufacturer keeps their prices at $100, the importer's cost is $120, the widget is still resold at $130.
consumer pays 100% of the tariff
Foreign manufacturer keeps price at $100, importer's cost is $120, resale price in increased to $150.
In practice, the cost of the tariff is split across more than one of these.
even split
Foreign manufacturer drops price to $93.333
Importer raises price to $136.666
Also: domestically manufacturered widgets priced from $100-120 this whole time, which importers may have previously ignored when the could get $100 foreign widgets, potentially become a viable option.
Maybe the foreign manufacturer will only go to $95 (importer's cost: $115), but the importer can also get domestic widgets for $115.
Furthermore:
Buying domestic widgets for $115 pays domestic workers, rather than shipping $95 overseas. That means more dollars in the local economy to buy widgets.