Geeyoung Min and Hye Young You have posted this draft on SSRN.  Here is the abstractL

Corporate political activity has become one of shareholders’ top concerns. We examine whether firms targeted by shareholder proposals show different campaign contributions and lobbying activities compared to non-targeted firms. We also ask whether different sponsors of shareholder proposals target different firms depending on the firms’ partisan orientation. Using data on S&P 500 companies during the period between 2007 and 2013, we find that firms that spend more on campaign contributions and lobbying are more likely to be targeted by shareholder proposals. After controlling for firms’ financial performance, governance characteristics and ownership structure, we also find that public pension funds and labor unions sponsors are more likely to target Republican-leaning firms, measured by the firms’ campaign contributions. This finding suggests that increasing corporate political activity can intensify a tension between management and public pension fund and labor union shareholders and lead to more activism by these shareholders.

(h/t Prof. Bainbridge)