California Center for Population Research

In May 2001 Senator Jim Jeffords left the Republican Party and tipped control of the U.S. Senate to the Democrats. This paper uses the surprise event to demonstrate what I term the "Jeffords effect": changes in the political landscape have large effects on the market value of firms. I use a firm’s soft money donations to the national parties as the measure of how the firm aligns itself politically. In this event study of large public firms, a firm lost 0.8% of market capitalization the week of Jeffords’ switch for every $250,000 it gave to the Republicans in the previous election cycle. Based on the point estimates, the stock price gain associated with Democratic donations is smaller than the loss associated with Republican donations, but the estimates are consistent with the coefficients being equal and opposite. The results withstand several robustness checks, and the effects appear to persist long after the event. The relationship between soft money and stock returns may or may not be causal: Soft money could be a proxy for how well each party’s policies suit a firm, or donations might affect how much help politicians give to a firm.