This paper is part of a larger project on the political determinants of labor market policy and outcomes in Latin America. In this paper, I focus on the case of Argentina. I argue that long-term patterns of economic policy, coupled with shorter-term concerns about political competition, have produced a non-monotonic relationship between the fate of organized labor and the Peronist Partido Justicialista. Drawing on the economic literature regarding the organization of the firm and incentives for vertical integration, I develop a theory that models when we should expect closest collaboration between labor-based parties and labor unions. Greatest gains for labor have come during Peronist resurgences and, counter-intuitively, during periods of internal division within the PJ while it was in power. Retrenchment on labor policy, on the other hand, has come during periods of Radical or military rule, when the Peronists were weakest, and in the presidency of Carlos Menem, when the Peronist hold on power was strong enough that the demands of organized labor could be marginalized in favor of export-oriented reforms. This paper finds that the most recent period of Argentine history, the post-Menem and post-crisis years of 2003 to the present, has been marked by a significant reactivation of organized labor union activity and important modifications in labor union bargaining and pension policy. This is puzzling, because the 1990s reforms were expected to leave unions so weakened that their incidence in the economic and political life of the nation would only further diminish. I argue that the recent resurgence in organized labor's institutional standing and economic gains is attributable to the internal competition within the PJ after the 2001-2002 crisis, which has created incentives for President Nestor Kirchner to cultivate ties to this traditional base of his party. ..PAT.-Unpublished Manuscript [ABSTRACT FROM AUTHOR]