The political economy of protection is a field within economics, but it has significant overlap with its sister discipline, political science. For a political economy of protection, one needs at a minimum two types of economic agents: political decision makers who provide protection, and economic agents who are protected or even actively seek protection. The typical political economy scenario leads to an economic outcome that is not Pareto-optimal: From a general welfare perspective, the political interaction is not desirable. An important task of political economy research is to explain why and how political interaction takes place. For the first part of the question, it appears clear that if protection is actively sought, the protection seeker intends to benefit from his activities. However, if the policymakers were truly interested in Pareto optimality and welfare maximization, they would refuse to protect. Hence a crucial assumption in the political economy literature is that the politicians’ objective function differs from the general welfare function. For the second part of the question, theoretical political economy models consider either the election campaign phase when politicians are eager to win a majority of votes (preelection models) or the phase when the politicians have been elected and may benefit from the spoils associated with holding office (postelection models). Whereas in the election phase, politicians have an incentive to cater to the interests of that part of the electorate that is considered pivotal for the election outcome, in the postelection phase they may be open to, for example, special interest group (SIG) influences from which they derive utility. A first wave of theoretical political economy models originates from the 1980s. Building on these early advances, more elaborate models have been proposed. The most prominent one is the Grossman–Helpman protection for sale (PfS) model. It delivers a postelection general equilibrium framework of trade policy determination. In this common agency model, industry interest groups act as principals and offer the government a menu of contracts of campaign contributions in exchange for trade policy. The PfS model predicts that industries that lobby for protection will obtain trade protection in equilibrium, whereas nonlobbying industries will face import subsidies. Numerous papers have evaluated the PfS model empirically and found that the implied weight on contributions in the governmental welfare function and the implied share of the population represented by lobbies are both very high. Remedies for this surprising result exist, but it has also been argued that the found empirical regularities may be spurious. At the beginning of the 21st century, the majority of political economy literature is still theoretical, but better data availability increasingly offers the opportunity to empirically test theoretical results. A number of challenges remain for the political economy literature, however. In particular, more work is required to better understand policymaker interests. Moreover, an incorporation of political economy aspects into the new trade theory models that allow for intra-industry trade and firm diversity appears to be a promising avenue for future research.