Contributor(s): Dr Jason Casellas, Dr Ursula Hackett, Mark Landler, Professor Stephanie Rickard | Jason Casellas is the John G. Winant Visiting Professor in American Government at the University of Oxford affiliated with Balliol College and the Rothermere American Institute. 

Ursula Hackett is Reader in Politics at Royal Holloway, University of London, and a British Academy Mid-Career Fellow. 

Mark Landler is the London bureau chief of The New York Times.

Stephanie J Rickard is Professor at the London School of Economics and Political Science in the Department of Government.