Literally, agenda means “things to be done”. In political terms, however, it has come to mean either a set of priorities for a particular organisation or – increasingly – the hidden motives of an individual or group.
Much like with bias, everyone has hidden motives – whether consciously or unconsciously. Accusing someone of “having an agenda” is therefore largely redundant.
There are, then, two ways in which historians might use the term effectively.
First: to explain the intentions of a particular group or individual.
More to the point, the conscious and explicit intentions, as outlined in a manifesto to the public, or internally through discussions and procedural documents. These intentions may not always be open to all – in which case “having an agenda” can return to its more effective meaning of a Machiavellian attempt to pursue hidden motives through political action. (See: the tobacco industry in the 1950s.) But the group or individual under discussion should be self-aware of these intentions.
Otherwise, we may be better off returning to “bias” as a way of explaining behaviours. Subconscious motives undoubtedly exist, and can be driving force behind a person’s actions. But to use the term “agenda” implies a set of clear goals or objectives – which is not always the case.
And, of course, agendas can often be counterproductive to the best interests of that individual. But this is a different discussion for a different time.
Second: as a conceptual framework for analysing the processes of policy making.
The political science approach to “agenda setting” can be a useful tool for understanding how and why certain issues come to be taken seriously by organisations and why (or why not) these organisation then try to do something about it.
These theories usually focus on the limits of organisation knowledge and ability to act. The various paradigms and historical circumstances in which actors operate, certain “problems” can only be seen as problems when they are articulated in ways that organisations can see. For example, “feminist” causes were not necessarily visible to British governments in the 1850s because there was not a language or appropriate advocacy group articulating these concerns in ways in which governments could respond. Another example would be that of “unemployment” – an economic concept that did not exist until the early twentieth century, and therefore could not be acted upon by concerted government policy before this point. Since then, economists and government departments actively seek out and monitor indicators of unemployment, and the issue has become one of electoral significance.
On this subject, good starting points are Kingdon’s Agendas, Alternatives and Public Policies and Pierson’s ‘Increasing Returns, Path Dependence, and the Study of Politics‘.