The article investigates the questions how and why, the European mainstream responds to the challenge of the right-wing populist parties (RPP), by analyzing the UK case. Using a mixed methodological approach, which includes the theoretical tools of historical institutionalism, Down's classification of the mainstream's strategies and Heinze's approach to analyzing the factors of its choice, we survey the strategic responses of the UK political mainstream (Conservatives and Labour), towards RPP (UK Independence Party). Findings suggest that the political mainstream could move from exclusion strategies, to predominantly inclusion strategies. In the UK case-cooptation of UKIP's policy positions with political and legal isolation. Transit to these strategies takes place under the influence of the electoral and ideological development of UKIP, the salience of migration issues, strategies of other mainstream parties and the historical conditions that define available options and shape the selection process, in the UKparty-based Euroscepticism.