An eye-opening portrait of Lincoln behind the scenes: Here is the career-long party politician whose brilliant coalition-building during the Civil War set the political foundation for emancipation and Union victory.

We know Lincoln as the eloquent, compassionate leader of a nation torn by civil war. But he had another, less visible side, equally central to his character and leadership: Lincoln was a master of party politics. Schooled as a Whig in the rough-and-tumble of Illinois electioneering in the 1830s, Lincoln skillfully navigated treacherous partisan crosscurrents and helped build the Republican party into a viable force. His decades of experience as a party leader proved invaluable to him as president and commander in chief during the Civil War.

Matthew Pinsker's groundbreaking history draws extensively on Lincoln's private correspondence to move beyond the marble icon and realize a flesh-and-blood character in Boss Lincoln. Behind closed doors he was shrewd and insistent, capable of deft manipulation, blunt intimidation, or thoughtful argument as needed. As a decision-maker he was attentive to detail but kept his own counsel and trusted his own acumen. His aides noted that in cabinet meetings Lincoln had the final say, and "there is no cavil." Devoted to elections, he kept careful, handwritten tallies of party turnout, even gifting one to Mary Todd, another partisan, during their courtship. His hymn to democracy at Gettysburg in 1863 carried a partisan message to the political leaders gathered there: The fight for the union would take place at the polls as well as on the battlefield. Boss Lincoln often sacrificed candor for purpose. He used his White House meeting with Frederick Douglass in 1864, ostensibly about emancipation, to send a message to radicals about his need for their support.

With emancipation and the war's outcome at stake, facing withering criticism from all sides, Lincoln won reelection by building a new political coalition through the Union party. Here was Boss Lincoln at his height, captured in absorbing detail in this indelible portrait of our greatest president.