There are various works that might be useful in this area.  This first one is specific to foreign-policy:  

https://www.surrey.ac.uk/politics/research/researchareasofstaff/isppsummeracademy/instructors%20/Levy%20-%20Psychology%20and%20Foreign%20Policy%20Decision-Making.pdf

Beach and Connolly's The Psychology of Decision-Making may be useful.  It appears to provide a brief review of many psychological constructs important to the topic.

The Psychology of Policy-Making by Dennis Chun-Lok Fung may also be useful to you, though it seems to cover a wide range of topics in a number of countries.

You also may simply want to review the general theories of group decision-making, management, and social psychology as they could be related to leaders who are devising policy.  To my non-expert mind, it seems that governmental policies could be made by groups of individuals who are influenced by a range of others (e.g., administration expectations, existing party platforms, lobbyists, and pressure from voters, among others) and then the methods of how decisions are made could be modified by awareness of outside views, the presence or lack of a group leader, etc. 

Related, perhaps not directly on topic, look up work by Dan Kahneman & Amost Tversky.

There work was more on "individuals" - but has clear implications

You might get some traction from David Stroh's Systems Thinking for Social Change and the literature included in his endnotes. Best.

The Identity Economics literature could be of interest:

https://www.cambridge.org/core/journals/american-political-science-review/article/a-model-of-social-identity-with-an-application-to-political-economy-nation-class-and-redistribution/7C3B4760571E6986D32973AF22060FFF

It describes the cognitive process of how individuals relate to each other and how they perceive themselves in relation to a broader group.

Additionally the following paper describes identity formation and the related psychological mechanisms, however more on a macro basis. This paper might be a good start though. 

https://www.researchgate.net/profile/Alexander_Wendt3/publication/243771961_Collective_Identity_Formation_and_the_International_State/links/56012a7408aec948c4fa9d0c.pdf

Hope this helps

Article Collective Identity Formation and the International State

The following publications may give some insights. More specifically in the first publication, chapter 3 (methodology) will give some insights.

1.Birner Regina, Surup Gupta and Neeru Sharma (2011) " The political economy of Agricultural Policy reforms in India - Fertilizers and Electricity for irrigation" Research Monograph, International Food Policy Research Institute, US

2.Bullock D.S (2012) " Dangers of using Political Preference Functions in Political Economy Analysis : examples from U.S.Ethanol Policy"  Paper prepared for presentation at the First AIEAA conference ' Towards a Sustainable Bio- economy: Economic Issues and policy Challenges' during 4-5 June 2012 in Trento, Italy