meetings and the 2002 MPSA meetings for their helpful comments, and our research assistants, past and present—Bill

We model political parties as adaptive decision makers who compete in a sequence of elections. The key assumptions are that winners satisfice (the winning party in period t keeps its platform in t + 1) while losers search. Under fairly mild assumptions about losers ’ search rules, we show that the sequence of winning platforms is absorbed into the top cycle of the (finite) set of feasible platforms with probability one. This implies that if there is a majority rule winner then ultimately the incumbent party must espouse it. However, we also establish, under weak assumptions about the out-party’s search, that the parties do not stabilize at the majority rule winner (should it exist). Thus full Downsian convergence is not predicted. We also show, both analytically and computationally, that the adaptive process is robust: in particular, if a majority rule winner “nearly ” exists then the trajectory of winning platforms tends to be “close ” to a trajectory of a process which actually has such a winner. 1 One of the most celebrated and cited5 books in political science is An Economic Theory of Democracy (Downs 1957). It routinely makes the discipline’s short lists of the most importan