President Harry Truman’s failure to pass a civil rights law was similar to the failure of the Wilmot Proviso because

a. it provided a political rationale for northern politicians to attack southern tyranny because the benefits of attracting new voters offset the cost of losing existing supporters.
b. it demonstrated that southerners were willing to use their institutional positions to fight any efforts at segregation.
c. it resulted in the destruction of the existing party system and generated significant political conflicts.
d. it highlighted the fact that the only way to end segregation and discrimination was with overwhelming majorities in both chambers of Congress.

a. it provided a political rationale for northern politicians to attack southern tyranny because the benefits of attracting new voters offset the cost of losing existing supporters.