Firms are loath to admit it, but pro bono is political, and in the vast majority of cases, it skews left. Arguably, pro bono is by nature liberal. Assisting the indigent, immigrants, murderers and the dispossessed—typical pro bono clients—is not for lovers of the status quo.

So what about conservative pro bono? Big firms have few qualms about advocating for economic conservatism. “We actively seek out libertarian cases,” says Michael Williams, a Kirkland & Ellis partner in Washington, D.C. Such cases often involve challenges to onerous regulations, he says.