Voting for Parties or for Candidates: Do Electoral Institutions Make a Difference?

Little is known about how electoral institutions systematically affect the level of incumbency advantage in legislative elections. In this paper, I analyze the Comparative Study of Electoral Systems (CSES) data to put the U.S. case in a comparative context and explore how electoral institutions aid or preclude incumbents from gaining an advantage. In particular, I study whether electoral systems affect the likelihood of party defection in lower house elections, a phenomenon closely related to incumbency advantage and defined as voting for a party other than one’s own. I find that the U.S. is not exceptional when it comes to party defection. Close to eighteen percent of the respondents in the U.S. claimed to have voted in 1996 for a congressman from a different party than the one they identified as their own, a number that falls midway within the distribution of the sample of countries analyzed. Furthermore, when focusing on countries with mixed electoral systems, I find that voters are more likely to place their votes based on candidate attributes such as incumbency status, as opposed to party affiliation, in elections were they cast a vote for a candidate rather than in proportional representation elections were they cast a vote for a closed party list. U.S. elections have long been considered unique, with its candidate-centered campaigns and high levels of incumbency advantage. In this paper, I set up to put the U.S. case in a comparative context and explore how electoral institutions aid or preclude incumbents from gaining an advantage. In particular, I study whether electoral systems affect the likelihood of party defection in lower house elections, a phenomenon closely related to incumbency advantage and defined as voting for a party other than ones own. Party defection seems to be a good proxy for incumbency advantage, on the grounds that if citizens are voting for a party other than their own it usually is because they are voting for the incumbent. A cursory look at the trends of incumbency advantage and party defection in the U.S., shows how closely these two phenomenons follow each other. When looking at the 36 countries included in the Comparative Study of Electoral Systems (CSES) dataset, I find that the U.S. is not exceptional when it comes to party defection. Close to eighteen percent of the respondents in the U.S. claimed to have voted in 1996 for a congressman from a different party than the one they identified as their own, a number that falls midway within the distribution of the sample of countries analyzed. However, this list includes countries with very different type of electoral systems. If we only look at elections in which voters cast votes for candidates instead of parties, the U.S. ranks close to the bottom. A quick look at the numbers seems to suggest that electoral systems have an effect on the level of party defection. On average, a vote casted in a single-member district elections has a 25 percent probability of being for a party other than the respondent’s own. Multiplemember district elections have a probability of party defection twelve percentage points smaller. Proportional representation elections with open party lists have a probability of party defection 4 percentage points higher than that of single-member district elections, on average. While proportional representation elections with closed party lists have a probability See Figures A.1 and A.2 in the Appendix. For details, see Table A.1. in the Appendix.