The Introduction introduces the central research questions of the study and summarizes the main arguments. It also lays out the research design and discusses the key concepts and how it measures them. Finally, it provides summaries of all of the chapters in the book.

Chapter 4 examines what led to the emergence of the strong parties that helped bring about democracy in some South American countries. It shows that during the late nineteenth and early twentieth century, relatively strong national parties arose in Chile, Colombia, and Uruguay, and, to a lesser extent, in Argentina and Paraguay, but not in the other countries of the region. Two main factors shaped party development during this period. First, strong parties emerged in countries that had intense but relatively balanced religious or territorial cleavages, where neither side of a cleavage clearly dominated the other. Religious issues, in particular, generated passions that politicians could exploit to build parties. Second, strong parties tended to emerge in countries that had populations concentrated in relatively small areas without major geographic barriers. In these countries, it was easier for politicians to mount national campaigns and for party leaders to develop organizations that penetrated the entire country. These arguments are explored through comparative statistics and brief case studies of party development in all ten South American countries.

Chapter 5 shows how the development of strong parties and professional militaries contributed to the emergence of enduring democracies in Chile and Uruguay. Both countries developed strong parties during the late nineteenth century thanks in part to the geographic concentration of the population and the existence of relatively balanced cleavages. During the nineteenth century, these parties at times sought power via armed revolts, but once the military professionalized, the opposition began to focus exclusively on the electoral route to power. This occurred in the late nineteenth century in Chile, but not until the early twentieth century in Uruguay. In both countries, opposition parties pushed for democratic reforms to enfranchise their supporters and level the electoral playing field. It was not until the ruling party split, however, that the opposition managed to enact major reforms, which occurred in Chile in 1890 and Uruguay in 1917. In both countries, strong opposition parties played a central role not only in the enactment of the reforms but also in their enforcement.

Chapter 1 lays out the central theoretical arguments of the book. It argues that three factors played a key role in the emergence of democracy in region: the professionalization of the military, the rise of strong opposition parties, and splits within the ruling party. It analyzes what led to the professionalization of the military and the rise of strong opposition parties and it shows how they led to varying regime outcomes in different South American countries. This chapter also discusses why existing theories of democratization cannot fully explain the emergence of democracy in the region

Chapter 6 examines how parties and the military shaped democracy in Argentina and Colombia. Both countries were ruled by authoritarian regimes in the nineteenth century that manipulated elections to remain in power. A strong opposition party, the Radical Civic Union, arose in Argentina in the 1890s and this party initially sought power through armed revolts as well as elections, but the professionalization of the military at the end of the nineteenth century made armed struggle futile. The Radicals pushed for democratic reforms but could not achieve them until a split within the ruling party led dissidents to come to power. After passage of the reforms in 1912, the Radicals won the presidency, but Argentina then lacked a strong opposition party, which undermined democracy in the long run. In Colombia, two strong parties arose during the nineteenth century and whichever party was in the opposition sought power at times via armed revolt. Colombia professionalized its armed forces in the early twentieth century, however, which forced the opposition to abandon the armed struggle. The opposition began to focus on the electoral path to power, but was only able to enact democratic reforms thanks to a split within the ruling party. In the wake of these reforms, Colombian elections became relatively free and fair, but the country's military was not strong enough to contain increasing regional violence, which undermined the country's democracy.

Chapter 7 explores the reasons why Brazil, Peru, and Venezuela experienced relatively stable authoritarianism during the early twentieth century. All three countries professionalized their militaries during this period, which helped bring an end to the frequent revolts that had undermined their prospects for democracy in the nineteenth century. None of the three countries developed strong parties, however. The absence of strong parties impeded democratization in several ways. First, party weakness allowed presidents to concentrate authority and extend their hold on power in some cases. Second, and even more importantly, the weakness of opposition parties meant that the opposition had little chance of winning elections or enacting democratic reforms, particularly in the face of widespread government electoral manipulation. As a result, the opposition frequently abstained from elections, which only deepened authoritarian rule in these countries. In some instances, the opposition also encouraged the military to intervene to overthrow the president, which undermined otherwise mostly stable authoritarian regimes.