This study investigates the impact of left political institutions on a nation's amount of poverty. Specifically, the analysis tests three possible causal relationships: whether left political institutions affect poverty separately from the welfare state, channeled through the welfare state, or combined with the welfare state. These relationships are tested with an unbalanced panel analysis of 16 rich Western democracies from 1967 to 1997 (N = 73, 74), two measures of poverty, and eight measures of left political institutions. The results demonstrate that the strength of left political institutions has a significant, powerful negative impact on poverty. Specifically, left political institutions partially combine with and partially channel through the welfare state. Voter turnout and the cumulative historical power of left parties entirely channel through the welfare state to reduce poverty. The percent of votes for left parties, the percent of seatsfor left parties, wage coordination, neocorporatism, gross union density and employed union density partially combine with and partially channel through the welfare state to reduce poverty. While the welfare state remains a crucial determinant of poverty, leftpolitical institutions are essential to explanations of the comparative historical variation in poverty.