John Coates has posted this draft on SSRN. Here is the abstract:

In Citizens United, the Supreme Court relaxed the ability of corporations to spend money on elections, rejecting a shareholder-protection rationale for restrictions on spending. Little research has focused on the relationship between corporate governance — shareholder rights and power — and corporate political activity. This paper explores that relationship in the S&P 500 to predict the effect of Citizens United on shareholder wealth. The paper finds that in the period 1998-2004 shareholder-friendly governance was consistently and strongly negatively related to observable political activity before and after controlling for established correlates of that activity, even in a firm fixed effects model. Political activity, in turn, is strongly negatively correlated with firm value. These findings — together with the likelihood that unobservable political activity is even more harmful to shareholder interests — imply that laws that replace the shareholder protections removed by Citizens United would be valuable to shareholders.