This paper deals with the effect ofconstitutional rules on agricultural policy outcomes in apanel of observations for more than 70 developing anddeveloped countries in the 1955-2005 period. Testablehypotheses are drawn from recent developments in thecomparative politics literature that see politicalinstitutions as key elements in shaping public policies.Using differences-in-differences regressions we find apositive effect of a transition into democracy onagricultural protection. However, this average effect maskssubstantial heterogeneities across different forms ofdemocracy. Indeed, what matters are transitions toproportional democracies, as well as to permanentdemocracies. Moreover, while the author does not detectsignificant differences across alternative forms ofgovernment (presidential versus parliamentary systems),there is some evidence that the effect of proportionalelection is exacerbated under parliamentary regimes, anddiminished under presidential ones.