One of Abraham Lincoln’s staunchest and most effective allies, Judge David Davis masterminded the floor fight that gave Lincoln the presidential nomination at the 1860 Republican National Convention. This history-changing event emerged from a long friendship between the two men. It also altered the course of Davis’s career, as Lincoln named him to the U.S. Supreme Court in 1862. Raymond J. McKoski offers a biography of Davis’s public life, his impact on the presidency and judiciary, and his personal, professional, and political relationships with Lincoln. Davis lent his vast network of connections, organizational and leadership abilities, and personal persuasiveness to help Lincoln’s political rise. When Davis became a judge, he honed an ability to hear each case with complete impartiality, a practice that endeared him to Lincoln but one day put him at odds with the president over important Civil War–era rulings. McKoski details these cases while providing an in-depth account of Davis’s role in Lincoln’s two unsuccessful campaigns for U.S. Senate and the fateful run for the presidency.