A recurring historical analogy in discussions of Brexit over the past few months has been the Conservative Prime Minister Robert Peel’s decision to back repeal of the Corn Laws in 1846. In lowering the price of grain, he split his party: an eventuality that Jacob Rees Mogg, among others, has warned Theresa May to avoid. At the very same moment Peel was driving a wedge through the Tories, though, another telling comparison to our present condition was taking shape across the Atlantic, where the future of U.S. land annexed from Mexico brought the question of slavery to the fore of electoral politics, and eventually led to the Civil War of 1861-65.
Like Europe, the ‘slavery question’ in the United States provides a case in point as to how the most divisive of issues can be shielded from party politics, yet how, with remarkable suddenness, they can come to occupy the centre of political debate.
To see battles over slavery and Europe as historical equivalents, of course, would be deeply problematic. Whatever the stakes in the current crisis the human toll pales into insignificance when set against the fate of the four million black southerners forcibly held as property across the US South. But the political dynamics, at least, bear some striking similarities.
Prior to 1846, slavery, much like the Europe question before the referendum, stood on the margins of American party politics. Despite the herculean efforts of black and white abolitionists to make it the great issue of the day, neither of the major political parties had any interest in challenging the status quo. Both the Whigs and the Democrats, after all, had been vying for votes from nearly all-white electorates in the North and South ever since the heyday of so-called ‘Jacksonian Democracy’ in the 1830s. To mobilise around either the expansion or extirpation of slavery would have alienated citizens in one section or the other.
Politicians for sure often had strong feelings about the enslavement of black southerners, and would say as much in their own states, but when it came to fighting national elections the parties were non-committal at best. It was a stance that all but guaranteed slavery’s perpetuation. No wonder many abolitionists saw party politics as a dead end.
Slavery, like Europe in British politics then, divided the parties internally prior to the 1850s, but did not automatically produce what political scientists refer to as a ‘realignment’. Attempts to turn American politics into a battle between anti-slavery and pro-slavery forces initially failed as the third parties of abolitionists and their southern critics flickered into life before quickly burning out… In a distorted way, such endeavours resemble the efforts of organizations like UKIP, insofar as they placed pressure on the major parties without forcing a redrawing of party lines. The survival of the Second Party System, as it was known, depended on silencing slavery as a subject of debate. When, from roughly the mid-1850s onwards, that no longer proved possible, the political landscape quickly changed beyond recognition. Abraham Lincoln’s election to the presidency in 1860 as the figurehead of a new, antislavery Republican Party underscored the transformation. Within a few months southern whites formed their breakaway slaveholding republic.
To understand the roots of the American Civil War we, therefore, need to explain that party realignment. How did slavery move from the margins of American party politics to become its central divide? In the simplest terms, historians have tended to fall into one of two camps to answer that question: ‘fundamentalists’, who see slavery slowly but surely undermining the foundations of the Second Party System, and the ‘revisionists,’ who blame either blundering politicians or political dynamics for the collapse.
The latter often hone in on the Kansas-Nebraska Act of 1854: legislation that opened new territory to slaveholders and prompted the formation of the Republican Party. At first glance, a brazen attempt to extend slavery, the measure, on closer scrutiny, can be seen as a ploy on the part of the northern Democratic Senator Stephen Douglas to resolve a political impasse in his party.
Eager to secure southern Democrats’ support for a transcontinental railroad from his home state of Illinois, he offered slaveholders the sop of new territory, while reasoning that soil and climate would prevent them from migrating in sufficient numbers to seize it. By making slavery extension a question for white voters in territories to determine themselves, Douglas believed the divisive issue could be depoliticized at the national level. The result was precisely the opposite: guerrilla warfare soon broke out in ‘Bleeding Kansas’ and within a few years electoral politics was pitting North v. South.
When it comes to the Civil War, I lean more towards the fundamentalist line. But if such categories were transposed to Brexit I’d be more inclined to revisionism. The Europe question has simmered in British politics since the 1970s, and has divided both major parties, but it required miscalculations on part of clever politicians to bring it to a raging boil. For Stephen Douglas and the Kansas Nebraska Act in 2016 read David Cameron and the referendum of 2016. Both were seemingly clever manoeuvres to resolve internal party conflict that had unforeseen consequences. The political fallout of Brexit, though, is harder to discern.
Even amid the current chaos, the national parties most united on Europe – UKIP, the Greens, and the Liberal Democrats – languish in the polls. No realignment has remade British politics into a struggle between pro- and anti-European parties, and for now at least, the old party lines just about hold. But will that be the case over the next few months? Once slavery did become the major issue in American politics between 1846 and 1854, it quickly tore apart the established parties. Nothing short of a revolutionary war could resolve it. That eventuality may be improbable here, but the party system we have grown up with may not long endure.
Andrew Heath is a lecturer in American History at the University of Sheffield, where he teaches a third-year special subject on the origins of the American Civil War. His book, In Union There Is Strength: Philadelphia in the Age of Urban Consolidation, will be published by University of Pennsylvania Press in February.
 Though ‘fundamentalists’ would quite rightly point out that Douglass was responding to pressure from his southern slaveholding colleagues in the Democratic Party.