This collective work offers a historical approach to the issue of voters' mobilisation and, through case studies, aims to expand the fi eld's research agenda by taking into account less familiar mobilising strategies from various groups or parties, both in Britain and the United States. Two different yet complementary approaches are used, one from the top down with political parties, the other from the bottom up with grassroots organisations, to analyze how these groups either (re-)connect citizens with politics or give birth to social movements which durably occupy and change the political landscape of the United States and Britain.