Pieces of the puzzle? Coalition formation and tangential preferences

The similarity of parties' policy preferences has long been considered an important determinant of whether they form a government coalition. That similarity has typically been assessed based on parties' respective locations in a policy space. The degree to which parties care about different issues may, however, also vary. Parties that care about different issues may actually be the most compatible partners, as their tangential preferences would allow them to engage in policy logrolling and enable them to preserve their distinctiveness in the eyes of voters. This analysis tests arguments regarding the role of tangentiality and its interaction with policy proximity on the party composition of governments formed in Western Europe from 1945 to 2019. The findings show that parties that emphasise the same issues are more natural coalition partners provided the ideological differences between the parties are sufficiently similar.