Daniele Caramani endeavors to document and explain the nationalization of party systems in Western Europe, the process by which the localized and territorialized politics of the nineteenth century (clientelistic politics dominated by local personalities) was replaced by nationwide functional alignments on the basis of class, in particular. This nationalization process was a crucial step in the structuring of party systems in the first century of electoral (democratic) politics. Although central to Western European electoral developments, it has received little scholarly attention, a gap that Caramani means to fill through empirical verification.

This study rests on an enormous data set, published separately by the author (Elections in Western Europe Since 1815, 2000), which encompasses electoral history in 17 Western European countries since 1815 and is disaggregated down to the constituency level. The data permit him to conduct extensive longitudinal analyses. He thereby studies territorial variations in electoral behavior (turnout and party support) within countries—across time, countries, and party families. The party systems of each of the 17 countries are analyzed in these terms, a project that comprises about one third of the book.

Caramani analyzes political cleavages as they are configured on the territorial space. The data attest to a general process of national political integration, a gradual homogenization of electoral behavior within countries and across Europe. Nationalization of electorates and party systems within each country, as well as the growing similarity between countries, he argues, largely resulted from the ascendance of the left–right class cleavage over the main preindustrial cleavages of religion, ethnicity, and so on; this ascendance was in turn the consequence of industrialization and the mobilization associated with the extension of suffrage. These processes led to liberal, conservative, and social democratic party families that were not territorially based. This process was relatively rapid up until World War I, after which political alignments were largely “frozen” from the 1920s on. On the other hand, regional cleavages have not entirely disappeared from European party systems. State formation and industrialization did not completely eliminate territorial diversity. Instead, several preindustrial cultural cleavages (religious and ethno-linguistic) have maintained at least some strength in European party systems despite general homogenization, resulting in the establishment and survival of religious, regional, and agrarian parties. Such parties have the highest levels of territoriality. The survival of such cleavages varies across countries according to patterns of state formation and nation building. Caramani traces the historical reasons for these developments, based on an admirably comprehensive grasp of the literatures on state building, secularization, industrialization, and democratization processes of European history.

But nationalization was also, as he further argues, the result of parties' competitive strategies as they tried to expand their reach throughout their respective national territories. In addition to the supremacy of functional left–right alignments, the nationalization of European electorates and party systems also resulted from electoral competition and parties' electoral strategies. In order to mobilize peripheral electorates, parties developed networks of local organizations controlled by national party headquarters. This happened early on; functional alignments arose even before mass suffrage, allowing liberal and conservative parties to cover national territories before suffrage extension. Liberals and conservatives penetrated each other's strongholds in search of votes. Competition guided strategic behavior of parties, starting with the advent of free elections, even before the rise of the social democrats or institutional modifications, such as proportional representation (PR). Thus, nationalization of electorates and party systems, Caramani argues, took place early as the original two-party families competed against each other, before the changes that previous literature identified as the main causes of nationalization: universal suffrage, PR, the Great Depression, and so on. Instead, nationalization dates back to the early stages of cleavage formation and party systems, with territorial diversity of voting behavior falling steeply until World War I and stabilizing thereafter. Only in a few cases, such as Belgium, Britain and Italy, does significant “re-regionalization” reappear after World War II.

The Nationalization of Politics rests squarely in the tradition of the cleavage model of party systems originally set out by Seymour Martin Lipset and Stein Rokkan (Party Systems and Voter Alignments, 1967). Caramani is deeply versed in the multidisciplinary literature relevant to this model, and his interpretation of the data makes a nuanced and welcome contribution to the party systems literature.