Research interests: American politics. Development of political institutions, particularly in the United States.  Political economy of public bureaucracies and government regulation, particularly regulation of health and financial products. 

Carpenter has recently launched a long-term project on petitioning in North American political development, examining comparisons and connections to petitioning histories in Europe and elsewhere. Together with colleagues at Harvard, Radcliffe and the Massachusetts Archives, he launched the Digital Archive of Massachusetts Antislavery and Anti-Segregation Petitions in 2015.