<p>While political history has plenty to say about the impact of Ronald Reagan''s election to the presidency in 1980, four Senate races that same year have garnered far less attention-despite their similarly profound political effect. <em>Tuesday Night Massacre</em> looks at those races. In examining the defeat in 1980 of Idaho''s Frank Church, South Dakota''s George McGovern, John Culver of Iowa, and Birch Bayh of Indiana, Marc C. Johnson tells the story of the beginnings of the divisive partisanship that has become a constant feature of American politics.</p><p><br></p><p>The turnover of these seats not only allowed Republicans to gain control of the Senate for the first time since 1954 but also fundamentally altered the conduct of American politics. The incumbents were politicians of national reputation who often worked with members of the other party to accomplish significant legislative objectives-but they were, Johnson suggests, unprepared and ill-equipped to counter nakedly nega