Scholars were quick to exploit the opportunities fo~ analysis offered by the new campaign finance data.Most of the early work focused on the question of how campaign spending influences election outcomes and the companion question of what determines how much money candidates raise and spend. A variety of models of campaign spending effects were proposed and examined. All took election outcomes to be a function of campaign spending and other variables but differed in how the outcome and spending variables were measured and in selection of control variables. These differences were reflected in several basic disagreements:i. On functional form. Proposed alternatives included linear functions (Shepard, 1977; Welch, 1974; Jacobson, 1976); semi-log (Welch, 1976); double-log (Welch 1974;Lott and Warner, 1974;Bental, Ben-Zion, and Moshel, 1977); and quadratic (Silberman and Yochum, 1978) for the money-votes relationship.2. On the measurement of relevant variables. For example, most models attempt to control the "normal vote"--the distribution of partisans--in a state or district. This has been approximated by party registration figures (Shepard, 1977; Welch, 1981;Caldeira and Patterson, 1982); district-level presidential votes (Welch, 1974(Welch, , 1981Silberman and Yochum, 1978), and previous votes for the same office or candidate (Jacobson, 1976(Jacobson, , 1978.3. On how the effects of incumbency are to be assessed. Incumbency is known to have a major impact on congressional election results and so, obviously, has to be taken into account. Most early models entered incumbency as a dummy variable (Welch, 1974; Jacobson, 1976;Shepard, 1977); others measured it as years in office, either logged (Giertz and Sullivan, 1977) or in quadratic form (Silberman and Yochum, 1978) to acknowledge diminishing returns.These early models generally overlooked the potential interaction between incumbency status and campaign-spending effects. But there was ample reason to expect that a given amount of spending would have different electoral effects for incumbents, challengers, and candidates for open seats. Later work confirmed that it did and indicated that the marginal returns on spending are much greater for challengers and other nonincumbents than for incumbents (Glantz, Abramowitz, and Burkhart, 1976; Jacobson, 1978;Silberman and Yochum, 1978).