Here’s a good rule of thumb for studying the history of American political parties: Forget what you know about the present. A century ago, Republicans were likely to be the country’s big-government progressives, its advocates of civil rights and social reform. Democrats were often small-government conservatives, especially in the one-party stronghold of the Solid South. The electoral map looked radically different, with a swath of blue below the Mason-Dixon line and a block of red in the Northeast. Just about the only things that have stayed the same are the party names: Democrat vs. Republican, locked in eternal electoral combat.

In “To Make Men Free,” Boston College historian Heather Cox Richardson sets out to tell half of the story about how we got from there to here. “The journey,” she notes dryly, “has not been straightforward.” The book offers a lively survey of Republican politics in all its diversity, from the “transformational presidency” of Abraham Lincoln (to borrow a 21st-century term) to the conservative ascendancy of Ronald Reagan. Along the way, Richardson aims to counter the claims of today’s tea party diehards, who insist that anyone to the left of Rand Paul is a RINO (Republican in Name Only). She makes a simple point but one that bears repeating: The Republican Party has had a long tradition of government activism, moderation and racial egalitarianism. The question of the 21st century is what happened to it.

As Richardson notes, the Republican Party’s first years were arguably its finest, at least as measured in terms of legislative accomplishment. Under Lincoln, Republicans helped to establish the nation’s first income tax, its first civil rights laws, its first federal draft and large-scale army, and its system of land-grant universities, in addition to passing the Homestead Act and winning the Civil War. Over the next century, Republican presidents continued this record of innovation. Theodore Roosevelt championed new labor laws and established food and drug regulation. Dwight Eisenhower launched the interstate highway system and poured money into public schools.

Richardson is less interested in how any of this happened — the backroom drama of whips and votes and party rule — than in the ideas behind the policies. Lincoln, in her view, established a Republican tradition that emphasized freeing workers and farmers from the tyranny of an ultra-rich elite. As time went on, however, Republicans developed a second ideological strain that prioritized small government, states’ rights and subservience to a wealthy business class. According to Richardson, it is in the tension between these “two fundamental beliefs, equality of opportunity and protection of property,” that the struggle for the soul of the Republican Party has taken place ever since.

To Richardson, the relationship between these two types of Republicanism has never been linear; the party did not slowly, inevitably, abandon Lincoln in favor of Reagan and the Koch brothers. Instead, party ideology has moved in cycles, with each activist president producing an equal and opposite reaction. Lincoln was followed by a group of small-minded, scandal-plagued Gilded Age successors. Then came Roosevelt, with his attacks on the “malefactors of great wealth,” followed by Calvin Coolidge, with his insistence that “the chief business of the American people is business.” Finally, after decades in the Democratic wilderness, Eisenhower pioneered a middle way, only to see subsequent generations follow a new course to the right.

‘To Make Men Free: A History of the Republican Party’ by Heather Cox Richardson (Basic)

There is no mistaking Richardson’s view about which of these paths has better served the county. For their founding father, progressive Republicans are given the great Lincoln, wartime visionary and martyr to the Union. The reactionaries get James Henry Hammond, an obscure, slave-owning senator from South Carolina. In an 1858 speech before Congress, Hammond argued that most human beings were mere “mudsills,” slaves and drudges put on Earth to support deserving men like himself. Hammond was not a Republican, but Richardson sees in his speech the foundations of the craven, money-worshipping culture that allegedly dominates today’s Republican Party. Beginning in the 1960s, she writes, “the wealthy men who hated the American consensus” rejected moderation and “revived the ideas of James Henry Hammond.” Like Hammond, they “didn’t care that a majority of Americans wanted an active government.”

Richardson is not wrong to see some resonance between the hierarchical worldview of the prewar South and the mind-set of mid-century conservatives, who often romanticized the Old South as a pastoral idyll. Even so, she sometimes overstates her case. Inequality may be on the rise today, but it’s a stretch to claim that in 2004 “the US economy, after years of Republican control, looked much like that of the American South before the Civil War.” Indeed, Richardson blames conservative Republican presidents for nearly everything that has gone wrong in the American economy since the Civil War. “As Republican policy shifted, and the machinery of government was enlisted to promote big business, wealth moved upward,” she writes, describing the party’s conservative swings. “And each time — in 1893, in 1929, and most recently in 2008 — these periods of reaction were followed by a devastating economic crash.”

For all her efforts to move beyond one-dimensional Washington bickering, Richardson ultimately finds herself caught in the partisan trap, blaming Republicans — albeit only the conservative ones — for ruining the economy, fomenting racism, damaging American democracy and betraying their progressive roots. “In this century, perhaps,” she concludes, “the Republican Party will find a way to stay committed to the ideals of its founders.” But she doesn’t sound terribly hopeful.

Beverly Gage is a professor of U.S. history at Yale University.