til all are exhausted and until the leadership has used every strategy . . . to ensure the greatest chance of its success." 69
In the Democratic Policy Committee study, the performance of every member of the Senate in 1964 was tabulated on all cloture votes since the atomic energy amendments of 1954. On the basis of this analysis, 55 senators were considered ready to invoke cloture on H.R. 7152 in the form it passed the House. Thirty-three senators were labeled as "reasonably sure against." This category included the bloc of 19 southern Democrats, all of whom were unquestionably against. 70 Finally, 12 senators were identified as "crucial." 71 This group included nine Republicans and three Democrats, and on their votes was thought to hang the question of cloture.
Summing up, the challenge confronting Mansfield and Humphrey could be understood by realizing that cloture on H.R. 7152 would require the affirmative vote of every senator identified in the Democratic Policy Committee study as "crucial," assuming no favorable votes were cast by the senators rated as "reasonably sure against" and all 100 senators voted.
The magnitude of this task, plus the simple fact that the Senate had never invoked cloture on any measure remotely associated with civil rights, stimulated considerable speculation that a compromise deal with the southern Democrats would be the only way to end the debate. But President Johnson's equally well-known opposition to such a solution, a position also taken by the crucial Republican members of the House, further clouded the outcome of the debate.
Mansfield, Humphrey, and Kuchel, the principal party leaders supporting the bill when the Senate began its debate, knew they faced a stiff test of legislative leadership. The difficulty of their assignment was summed up with this question: Could they control the debate in a manner which permitted senators, both collectively and individually, to exercise independent judgments on the controversial issues without sacrificing the substantive objectives which President Johnson and the House of Representatives considered essential?