The above graph comes from Adam Bonica, a Ph.D. student in political science at NYU. Using political donations to estimate ideology, Bonica plots the ideological distribution of the members of various corporate boards. He writes:
bq. These results challenge conventional beliefs about the political leanings of corporate leaders. Republicans have long been seen as the party of big business. To whatever extent this label should apply, it probably owes more to the party’s policies than the composition of its support base. Although board members from some sectors exhibit conservative allegiances—notably the oil, gas, and coal industries—most corporate boards are either dispersed across the ideological spectrum, or seem to have aligned with the left, as is the case of many of the growth stories of the new economy.
He then offers two hypotheses about the effects of Citizens United. Here is one:
bq. Republicans will not be the clear beneficiaries of Citizens United.
See his post here.