Writing mote than 20 years ago, W. P. Welch used a probit model to attempt to isolate the effect of campaign contributions on roll-call voting from other influences like the legislator's constituency, party, and ideology. The literature on the relationship between campaign contributions and legislative votes is extensive, with often-inconsistent findings. It is typically the case that contributions from interested groups are correlated with roll-call voting favorable to the contributor's interests. Studies that include a wider range of variables find that this relationship is not so simple. Interest groups contribute to members who are already often predisposed to support their position. If the group has a local presence, then members may be voting with the group because of constituency pressures. Party and ideology also must be factored into the analysis (Ansolabehere, Figueiredo, and Snyder 2003; Chin 2005; Roscoe and Jenkins 2005; Wawro 2001).
Welch's (1982) article presents a conceptual framework in which to consider the exchange of campaign contributions from an interested group for votes by legislators on past or future legislation. Welch links this transaction to what he labels "exchange theory." His framework includes assumptions that were well grounded in the understanding of congressional elections and campaign finance at the time. His overall conclusion was that "although contributions are significant, they were the least important determinant of legislative voting" (Welch 1982, 493). What other determinants were more important? He finds that variables like dairy production (a measure of constituency interest), ideology, and party are all stronger predictors of the vote on milk price supports than campaign contributions.
Welch's article is cited in sociology, economics, and political science journals. While this essay will explain its central argument about the relative influence of campaign contributions on roll-call votes and vice versa, it is also the case that Welch is frequently cited in studies of legislative behavior, interest groups (especially agricultural groups), and, more broadly, about campaign finance.
Context of Welch's Article
The conventional wisdom "that interest groups 'buy' influence by contributing to political campaigns" motivates Welch's analysis (Welch 1982,487). At the time of publication, the issue of campaign contributions from interest groups had become more salient because of the Watergate investigation of a botched burglary of the Democratic National Committee at the Watergate Complex in Washington, D.C. The investigation had uncovered large illegal contributions to the Committee to Reelect the President (CREP) during the 1972 election cycle (Corrado and Mann et al. 1997,283). Watergate galvanized Congress to reform the way federal elections are financed. New regulations in the form of a set of 1974 amendments to the Federal Election Campaign Act (FECA) imposed contribution and spending limitations, mandated disclosure, and established an enforcement agency, the Federal Election Commission (FEC), to over see the new regulations. Welch indirectly mentions FECA in his opening paragraph when he states that the public belief that interest groups buy influence is a reason "for Congress either publicly to finance congressional campaigns or to place a limit on the amount of monies that a candidate may receive from political action committees" (Welch 1982, 178).
While Welch finds only modest independent effects for campaign contributions, in his words "not a major influence," he does find that those who received contributions in the 1974 election cycle were more likely to vote for higher milk-price supports in 1975. Similarly, those who voted with the milk producers in 1975 were more likely to receive contributions from the Dairy PAC during the 1976 election cycle. Consistent with what we know about legislative specialization and interest-group behavior, he finds that contributions to the Agriculture Committee members were higher, other things being equal. …