Political Parties and Policy Outcomes. Do Parties Block Reforms?

I propose a model of legislative bargaining among endogenous political parties over multiple policy dimensions. I provide a characterization of (i) the partition of the legislature into parties, (ii) the policy reforms that parties propose (if any), and (iii) the policy outcome attained from these proposals. I show that - depending on the position of the status quo - either (1) the presence of parties does not affect the policy outcome and a median voter theorem holds, or (2) a party representing legislators with extreme and opposite political views - i.e., a coalition of extremes - can successfully block reforms that would be feasible if parties did not exist. Lastly, I show that the extent to which the existence of parties can increase the set of possible policy reforms is severely limited or null.