Tariff
A tariff is called an optimal tariff if it's set to maximize the welfare of the country imposing the tariff. It is a tariff derived by the intersection between the "trade indifference curve" of that country and the offer curve of another country. In this case, the welfare of the other country grows worse simultaneously, thus the policy is a kind of "beggar thy neighbor policy". If the offer curve of the other country is a line through the origin point, the original country is in the "condition of a small country", so any tariff worsens the welfare of the original country.
Tariff in United States history
Democrats were divided on the issue, in large part because of pro-tariff elements in the Pennsylvania party who wanted to protect the growing iron industry, as well as pockets of high tariff support in nearby industrializing states. However President Grover Cleveland made low tariffs the centerpiece of Democratic Party policies in the late 1880s. His argument is that high tariffs were an unnecessary and unfair tax on consumers. The South and West generally supported low tariffs, and the industrial East high tariffs. Republican William McKinley was the outstanding spokesman for high tariffs, promising it would bring prosperity for all groups.