Rising incumbency advantages in U.S. House elections have prompted a wave of new electoral laws, ranging from campaign nance regulations to term limits. We test a central claim for these reforms { that the incumbency advantage re°ects the collective irresponsibility inherent in legislatures. We study incumbency advantages for all state executive elections from 1942 to 2000 and contrast that with incumbency advantages in state and federal legislative elections. We nd that incumbency advantages for state executives and for legislators are similar in magnitude and have grown at the same rate over the last 60 years. If anything legislators have lower incumbency advantages than state executives. This nding reveals that the incumbency advantage is not unique to legislatures and that theories of incumbency advantages based on redistricting, legislative irresponsibility, pork barrel politics, and other features of legislatures do not explain the incumbency advantage. Some time in the late 1960s, congressional scholars began to note the increasing vote margins of U.S. House incumbents. By the mid-1970s a full-blown debate about the magnitude and sources of the incumbency advantage in US House elections had emerged. The list of potential causes is many { redistricting, congressional-bureaucratic relations, pork barrel spending, campaign nances, and declining party attachments. Broadly speaking, the debate over the sources of the incumbency advantage points either to factors that are distinctive to legislative politics, such as pork barrel politics and redistricting, or to factors that likely a®ected all o±ces, most notably the decline of party attachments or the growth of government generally. The conventional wisdom holds that legislative incumbents have uniquely high electoral advantages for two reasons. The rst is that many things that are thought to a®ect reelection rates are unique to legislatures. The most important of these are redistricting and seniority. Cox and Katz (2002) argue that the redistricting revolution caused the rise of incumbency advantages after the 1960s, because district lines can now be drawn to prevent competition. McKelvey and Reizman (1992) argue that seniority systems create a disincentive for voters to select someone else. Power within the legislature is tied to seniority, and as a legislator climbs the seniority rank the voters that legislator represents will bene t. Because all incumbents have some seniority no voters want to turn out their incumbent in the place of a new person, who will be the lowest ranked legislator. A second reason that legislators are thought to have especially large incumbency advantages is the lack of collective responsibility. Executives are held accountable for the broad performance of their agencies. Governors are responsible for economic performance; attorneys general, for crime; and so forth. Executives are also accountable for their actions: an executive decision is the decision of the individual politician. Legislatures, by contrast, are collective bodies. It is hard to know who in the legislature is responsible for a weak economy or a high crime rate. Party leaders can also coordinate legislators so that an individual legislator does not have to cast a vote that is particularly unpopular in the individual's
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