There are two sets of data exploring people's attitudes in Northern Ireland towards different types of Brexit and their possible consequences on political stability and peace. The survey data is a representative sample of 1,012 people from across Northern Ireland were interviewed by Ipsos-MORI in face-to-face computer-assisted interviews between 9 February and 12 March 2018. A two-stage sampling design was used, with random selection of geographic sampling points and quotas set for each sampling point based on the latest socio-demographic census estimates to ensure that the respondents were statistically representative of the Northern Ireland population regarding traits such as age, gender, religion of origin, geographical location, and social class. The deliberative forum data studies 48 people from across Northern Ireland took part in a deliberative forum in which they received expert presentations and discussed the possible impact on Northern Ireland of the UK’s exit from the EU. This deliberative forum took place on 10 February 2018 at the Clayton Hotel in Belfast. Ipsos MORI recruited the 48 participants to be broadly representative of the Northern Ireland population in their socio-demographic backgrounds and geographic residences. Importantly, the sample was broadly balanced between those who had voted Leave and those who had voted Remain in the 2016 referendum. The participants’ roundtable discussions in the morning and afternoon were recorded and transcribed. Participants also completed questionnaires, from which survey data are provided. A follow up survey experiment was conducted in 2019 to test the effect of imagined dialogue on inter-group attitudes. In the first wave (March-April 2019), the experimental treatment involved participants engaging in an imagined conversation about a controversial political issue with someone holding the opposite view; participants randomly assigned to the control condition were asked to imagine having a conversation about a benign non-political issue with someone holding an opposite political viewpoint. The survey experiment was conducted using representative samples in three political contexts: Northern Ireland (unionists/nationalists; N = 1,263), Great Britain (Remainers/Leavers; N = 1,879), and the USA (pro-life/pro-choice; N = 1,217). A second wave of the experiment (June-July 2019) used the same design but addressed partisan divisions rather than divisions over political issues in Northern Ireland (SF/DUP supporters; N = 806), Great Britain (Conservative/Labour supporters; N = 839) and the USA (Democrats/Republicans; N = 836).Peace and stability in any society is dependent upon citizen acceptance of the legitimacy of political and legal arrangements, and particularly so in Northern Ireland where peaceful politics is a recent outcome of a long and difficult 'peace process'. Knowing the likely level and intensity of perceived illegitimacy (non-acceptability) of different possible border arrangements after the UK leaves the EU would provide policy makers with crucial evidence when evaluating the relative merits of different border options, particularly with respect to the criteria of political sustainability and likely impact on peace and stability in Northern Ireland. With Northern Ireland's politicians engaged in political campaigning in an Assembly election and likely impending inter-party talks to re-establish a power sharing executive, it is arguably particularly important that there is a systematic reporting of the considered views of citizens on this crucial issue of the UK's exit from the EU. We conduct two "deliberative democracy" exercises which allow Northern Ireland citizens the space and relevant information to consider the challenging issue of Brexit and the border. Once they have become informed about the issues and reflected upon them, we ask the citizens to put forward their own views. We are focused on answering the following questions. How difficult would it be for Catholics/nationalists to accept a policed North/South border and what level of protest would they condone? How difficult would it be for Protestants/unionists to accept a policed East/West border and what level of protest would they condone? We seek to provide policy makers with evidence-based answers to the these questions. This evidence will prove to be especially useful when policy makers are considering the likely implications of the post-Brexit border for peace and stability in Northern Ireland. We generate a report which summarises our key findings and presents our key evidence. We also produce a short animated film which gets across to the viewer in a dramatic, simple and exciting way our key findings. We engage enthusiastically in submissions to the key committees, bodies and specific politicians who have responsibility for negotiating the UK exit from the EU. We contribute to their work by highlighting the likely implications, for peace and stability in Northern Ireland, of pursuing certain post-exit border scenarios.

Cross-sectional survey (N=1,012): A two-stage sampling design was used, with random selection of geographic sampling points and quotas set for each sampling point based on the latest socio-demographic census estimates to ensure that the respondents were statistically representative of the Northern Ireland population regarding traits such as age, gender, religion of origin, geographical location, and social class. Deliberative forum data: 48 people from across Northern Ireland took part in a deliberative forum. Ipsos MORI used quota sampling to ensure the sample was broadly representative of the Northern Ireland population in terms of age, gender, community background, geographical location, social class, and 2016 referendum vote choice. The participants’ roundtable discussions in the morning and afternoon were recorded and transcribed. Participants also completed questionnaires, from which survey data are provided. Experimental data (N = 6,840 across two waves): Participants in Northern Ireland, Great Britain and the USA were recruited via the online panels of survey companies based in each location, with quotas to ensure the representativeness of each sample.