Model-Based Pre-Election Polling for National and Sub-National Outcomes in the US and UK

We describe a strategy for applying multilevel regression and post-stratication (MRP) methods to pre-election polling. Using a combination of contemporaneous polling, census data, past election polling, past election results, as well as other sources of information, we are able to construct probabilistic, internally consistent estimates of national vote and the sub-national electoral districts that determine seats or electoral votes in many electoral systems. We report on the performance of three applications of the general framework conducted and publicly released in advance of the 2016 UK Referendum on EU Membership, the 2016 US Presidential Election, and the 2017 UK General Election.