Reading about the history of the early American republic is a curious experience. The United States before the Civil War has the same basic ingredients as the country we live in – the same cities and states (though not as many of them), the same presidents and senators – but they seem to be put together differently. Words change meaning: Jefferson’s Republicans are not Lincoln’s Republicans, or Reagan’s; Jackson’s Democrats are not Lyndon Johnson’s. As on the tree of life, there are early species that have disappeared – Federalists, Whigs, Anti-Masons, Know-Nothings. There is a whole political slang, once vivid, now quaint – Loco Focos, Hunkers, Bucktails, Wide-Awakes. There are questions that once convulsed the nation, now almost too abstract and intricate to unravel: the embargo, the Bank of the United States, the American System, nullification. It is tempting to retreat to the more familiar pastures that come before Adams and after Buchanan: the grand victories of the Revolution, or the tragic sufferings of the Civil War.

The achievement of Sean Wilentz’s “The Rise of American Democracy” is to make that occluded period come clear – and more important, to show why it still matters. In 800 packed pages, he guides the reader down all the broad and narrow byways of American politics from 1800 to 1860. The result is a text too dense with information to be an easy read, though never clumsily written or unnecessarily difficult. Its density is justified by the large idea that organizes and sustains the narrative: that the period from “Jefferson to Lincoln,” as the subtitle has it, was the seedbed and proving ground of the American vision of democracy.

Before 1800, the United States was still an ex-colony, informed by old ideas of deference, in which John Adams could dread the idea that “every man who has not a farthing will demand an equal voice with any other.” By the time of the Gettysburg Address, Lincoln could define the American ideal as “government of the people, by the people, for the people,” and ask the people themselves to shed blood for it. The story of Mr. Wilentz’s book is how that immense distance was crossed.

One problem raised by the subject is how to write about democracy democratically – that is, without restricting the historian’s focus to elite figures and formal political discourse. In other words, as Mr. Wilentz writes in his introduction, he has to avoid giving the impression “that presidents and other great men were solely responsible for the vicissitudes of American politics,” while still acknowledging “that some individuals have more influence on history than others.” His solution, which distinguishes “The Rise of American Democracy” from earlier great studies of the period (such as Arthur Schlesinger Jr.’s “The Age of Jackson”), is to show that politics is a complex system in which the actions of ordinary citizens can provoke and constrain those of presidents.

Yet Mr. Wilentz avoids the appearance of simply dressing up a political narrative with episodes from social, religious, and economic history, as historians often do in an attempt to seem populist. Rather, he shows that, in the early Republic, all these kinds of history are essentially, genuinely political: “Americans perceived … social changes primarily in political terms and increasingly saw them as struggles over contending ideas of democracy.” When our forefathers argued about tariffs and monetary policy, or immigration and slavery, they were always really arguing about democracy, and how to preserve and extend it.

As an example of Mr. Wilentz’s catholic definition of politics, take David Walker. In 1830, Walker, a free black citizen of Boston, published an explosive “Appeal … to the Coloured Citizens of the World, but in Particular, and Very Expressly, to Those of the United States of America.” In apocalyptic language influenced by the Book of Revelations, Walker viciously attacked slavery and white racism, holding out the hope that a slave insurrection or civil war would finally cleanse America of its guilt. More inflammatory still, he managed to get his appeal smuggled into Southern states and distributed to slaves.

When this was discovered, the mayor of Savannah demanded that the mayor of Boston stop Walker’s press, which he refused to do. The controversy helped to expose sectional divisions about slavery, radicalize white abolitionists like William Lloyd Garrison, and undermine the national conspiracy of silence that had been institutionalized in the Missouri Compromise a decade before.Walker, as disenfranchised an American as one could hope to find, still made a crucial contribution to political life.

This made him representative of the times. In 1828, Andrew Jackson had swept into the White House on a tide of democratic enthusiasm, buoyed by the new Western states, where old class and sectional rivalries were being transformed. Jackson’s own career epitomized the contradictions of democracy in the early Republic. His popularity came from his victory in the Battle of New Orleans in 1815, the concluding act of a war that, while pointless, helped to promote a new spirit of American nationalism. On the first day of his presidency, the White House was flooded with well-wishers, to the dismay of Washington society: “a rabble, a mob, of boys, negros, women, children,” in the words of one appalled hostess. The promise of Jackson’s new party, which became known as the Democracy,was to break the power of elites, like the wealthy financiers behind the Bank of the United States, and restore the egalitarian promise of the Declaration of Independence.

Yet Jackson, the tribune of the people, was also a slaveholder. He oversaw the expulsion of the Cherokees from Georgia, in which thousands died on the infamous Trail of Tears. He instituted the “spoils system” of party-based patronage, which made government more beholden to special interests. Democracy, even in the high Jacksonian period, was an idea full of contradictions. The country would not give it up – after Jackson, there was no more room in politics for the aristocratic New England Federalists – but it could still be contested and redefined.

The Whig Party, which unseated Martin Van Buren in the election of 1840, triumphed by advancing an alternative vision of democracy, one in which moral improvement and middle-class advancement were the engines of equality. This vision made the Whigs more conservative than the Democrats from one point of view, but more progressive from another: Lincoln, the great emancipator, began his political life as a Whig.

Finally, of course, it was slavery that most powerfully challenged American democracy. The last third of Mr. Wilentz’s book is dominated by the political struggles that strained and finally broke the union: over the Mexican War, the Fugitive Slave Act, Bleeding Kansas, and the Dred Scott decision. Even here, however, Mr. Wilentz shows that the debate was always cast in terms of democratic rights. An increasingly anti-slavery North confronted a South convinced that democracy for whites depended on the enslavement of blacks.

Mr. Wilentz does not discuss the war itself, ending his narrative with the firing of the first shot on Fort Sumter. But his epilogue concludes with a remarkable image: a photograph of the mixed-race jury empaneled after the war for the trial of Jefferson Davis, which never took place. The picture, Mr. Wilentz writes, silently “affirms that the revolution caused by the rise of American democracy had created realities and possibilities scarcely imaginable” earlier. Mr. Wilentz’s major work helps us to imagine that revolution more completely than ever before.

akirsch@nysun.com