A radical and a neoconservative change their political stripes.America at the Crossroads: Democracy, Power, and the Neoconservative Legacy, by Francis Fukuyama, New Haven: Yale University Press, 226 pages, $25 Power and the Idealists: Or, the Passion of Joschka Fischer and Its Aftermath, by Paul Berman, Brooklyn: Soft Skull Press, 311 pages, $23.95The 20th century produced a glut of political converts, St. Pauls in search of ideological roads previously untaken. Even today, in an allegedly post-ideological age, converts are plentiful.Two recent books, Francis Fukuyama's America at the Crossroads and Paul Berman's Power and the Idealists, describe parallel progressions. Fukuyama, once a...