We present a model of electoral competition with endogenous platforms and campaign spending where the division of voters between impressionable and ideological is also endogenous and depends on parties’ strategic platform choices. Our approach results in a tractable model that provides interesting comparative statics on the effect of recent technological advancements. For instance, we can accommodate a new justification behind the well-documented simultaneous increase in campaign spending and polarization: an increase in the effectiveness of electoral advertising, or a decrease in the electorate’s political awareness, surely increases polarization and may also increase campaign spending.