Reaching across the aisle to block reforms

I propose a model of legislative bargaining among endogenous coalitions over multiple policy dimensions. I provide a characterization of (i) the partition of the legislature into coalitions, (ii) the policy reforms that coalitions 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 coalitions does not affect the policy outcome and a median voter theorem holds, or (2) an alliance among legislators with extreme and opposite political views—i.e., a coalition of extremes—can successfully block reforms that would be feasible if legislator could not coalesce. Lastly, I show that the extent to which the existence of coalitions can increase the set of possible policy reforms is severely limited or null.