ABSTRACT
Interest groups and political parties often forge close ties. Many business groups contribute heavily to Republican candidates and party committees and, in some cases, even run advertising campaigns independently to help party candidates. Labor unions routinely mobilize voters to support Democratic candidates, using volunteers who operate phone banks. However parties and interest groups have different goals and incentives, and they sometimes find themselves on opposite sides of issues. In late 2005, the Republican leadership pushed a bill that would require businesses to verify that all of their workers are in the United States legally and would increase the penalties for hiring illegal employees. The bill was popular with groups within the Republican coalition that opposed immigration, however, business groups argued that the bill imposed an unreasonable cost on companies. The U.S. Chamber of Commerce and other business groups mounted a major effort to kill the bill, working against the same party leaders with whom they usually cooperate.1 The conflict exemplifies the complicated relationship between interest groups and political parties: one of frequent cooperation but occasional conflict.
