The most analyzed choice situation by electoral researchers is at the ballot box. In partially-contested elections, such as in Britain or Spain, voters cannot vote for all parties in every region or constituency. We present a modeling approach to study rational voting behavior that integrates such heterogeneous ballots and takes voting for the numerous parties therein seriously. The empirical application to the 2015 British Election demonstrates substantial insights not found when neglecting ballot composition heterogeneity or applying existing approaches
