'extremely impressive contribution to our understanding of the party's creation ... Gienapp has done exemplary work in unravelling the operation of American state and national politics in these years of upheaval ... He has given chronological and analytical clarity to a very confusing period, and has done so with vigour, readability and exhaustive research. His study is one of the most impressive works of scholarship among scores of books published in the last two decades on mid-19th-century American politics.' Times Higher Education Supplement