Traditional power indices are not suited to take account of explicit preferences, strategic interaction, and particular decision procedures. This paper studies a new way to measure decision power, based on fully specified spatial preferences and strategic interaction in an explicit voting game with agenda setting. We extend the notion of inferior players to this context, and introduce a power index which - like the traditional ones - defines powers as the ability to have pivotal influence on outcomes, not as the (often just lucky) occurrence of outcomes close to a player's ideal policy. Though, at the present state, formal analysis is based on restrictive assumptions, our general approach opens an avenue for a new type of power measurement
