David Hare's play about an American college professor who wrangles politically (and almost romantically) with the father of her British fiancé, may not be one of his very best. But how many other dramatists write plays that actually engage the public issues of the moment (in this case, the Iraq war); can give intellectual arguments such life onstage; believe so passionately that politics are an inextricable part of the larger human drama? Bill Nighy, as the unapologetic liberal, overshadows Julianne Moore, in her Broadway debut as the Bush-supporting professor, but not enough to disrupt the crisp clash of ideas.