A FEW MONTHS AGO, those on the American Left exhaled when Barack Obama was reelected President; they seemed to experience less joy than relief. Those on the Right, however, were plunged into agony. Tonight, as they tough out another State of the Union address by their Democratic nemesis, prick up your ears to the boom mics in the House: the grinding of teeth should be audible.

It’s been a rough run for the GOP in recent years. By 2008 George W. Bush was toxic. Next in line was John McCain, whom they never quite trusted but did their best to rally behind. Then came Mitt Romney, which was, clearly, no love affair. The resulting fractious debate inside the Republican Party — including recent news that Karl Rove’s Crossroads GPS is forming a super PAC called “Conservative Victory Project” to quash the Tea Party insurgency inside the GOP — has laid bare the fissures in the coalition the Republicans have successfully held together for so long. Its alliances seem under pressure to a degree unprecedented in recent times, since the Southern strategy began the great migration of that region’s white conservatives into the party.

South Carolina Senator Strom Thurmond was famously the bellwether of this shift. He broke with the Democrats in 1948 to mount a quixotic run for president on a segregationist platform against his party’s incumbent, Harry Truman, because of Truman’s advocacy for civil rights legislation. But Thurmond was more than a mere racist. As historian Joseph Crespino argues in Strom Thurmond’s America, Thurmond incarnated the confluence of business interests, anticommunism, and states rights that motivated the Republican Party in the post-civil rights era, epitomized by Reagan and carrying through, perhaps in a new state of uncertainty, the present day.

Thurmond’s remarkable longevity — born 1902, died 2003 — allows Crespino to draw together in one narrative a century of evolution in American society and politics. Thurmond’s father was the personal lawyer of the virulently racist politician “Pitchfork” Ben Tillman; after Thurmond’s death, Essie Mae Washington-Williams, the African-American daughter Thurmond never acknowledged (and who herself died just this month), witnessed the reinscription of a statue of her father on the grounds of the South Carolina State Capitol to reflect the truth. The words “Father of Four” were changed to “Father of Five.” Crespino offers an illuminating, detailed account of Thurmond’s early years in South Carolina as well the period in which he occupied a central yet underacknowledged role in American politics. The book shows how political exigencies, rash acts, and deeply held beliefs commingle, with tactics and impulses becoming strategy and necessity before ultimately reifying into history.

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Domenick Ammirati: Why did you choose Strom Thurmond as a subject?

Joseph Crespino: Thurmond fits so uneasily into the kinds of stories we tell about modern conservatism. Many people on the Left want to reduce the history of conservatism’s rise to...