American liberals have a habit of withdrawing into cynicism and ennui at the most inopportune moments. The 2000 presidential election, and subsequent recount, was one such moment. The most die-hard reaches of the left, deeming the Democratic Party hopelessly corrupt, rallied to Ralph Nader’s fulsome populist denunciation of Al Gore’s subservience to the corporate agenda. Among more moderate quarters, an attitude of wry detachment prevailed. (“G.O.P.-lite, Democrat-lite,” sighed Frank Rich, “For the 95 percent of the country unwilling to go for Ralph Nader or Pat Buchanan, that is the choice, it always has been the choice, and it will still be the choice on Nov. 7.”) Those liberals who did see something large at stake took on an almost apologetic tone, conceding the lack of...