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. Tuesday Night Massacre 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. 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 negative emotional appeals to the “politically passive voter.” Such was the campaign of the National Conservative Political Action Committee (NCPAC), the organization founded by several young conservative political activists who targeted these four senators for defeat. Johnson describes how such groups, amassing a great amount of money, could make outrageous and devastating claims about incumbents—“baby killers” who were “soft on communism,” for example—on behalf of a candidate who remained above the fray. Among the key players in this sordid drama are NCPAC chairman Terry Dolan; Washington lobbyist Charles Black, a top GOP advisor to several presidential campaigns and one-time business partner of Paul Manafort; and Roger Stone, self-described “dirty trickster” for Richard Nixon and confidant of Donald Trump. Connecting the dots between the Goldwater era of the 1960s and the ascent of Trump, Tuesday Night Massacre charts the radicalization of the Republican Party and the rise of the independent expenditure campaign, with its divisive, negative techniques, a change that has deeply—and perhaps permanently—warped the culture of bipartisanship that once prevailed in American politics.