英语摘要：How do foreign interests influence the policy determination process? How is trade
policy affected? What are the welfare implications of such foreign influence? In this
paper we develop a model of foreign influence and apply it to the study of optimal
tariffs. We develop a two-country voting model of electoral competition, where we allow
the incumbent party in each country to take costly actions that probabilistically affect
the electoral outcome in the other country. We show that policies end up maximizing
a weighted sum of domestic and foreign welfare, and we study the determinants of this
weight. We show that foreign influence may be welfare-enhancing from the point of view
of aggregate world welfare because it helps alleviate externalities arising from crossborder
effects of policies. Foreign influence can however prove harmful in the presence
of large imbalances in influence power across countries. We apply our model of foreign
influence to the study of optimal trade policy. We derive a modified formula for the
optimal import tariff and show that a country’s import tariff is more distorted whenever
the influenced country is small relative to the influencing country and whenever natural
trade barriers between the two countries are small. We also show that the viability of
free trade agreements can be hampered by large imbalances in power across countries.