At a fundraiser on Tuesday, former vice president Joe Biden invoked Southern segregationists James Eastland and Herman Talmadge as examples of past Senate colleagues with whom he could work. “At least there was some civility,” he remarked of the Senate in the 1970s and 1980s. “We got things done.” Biden had already written about Eastland with some affection in his memoirs and brought him up at a stump speech in 2017 to express similar nostalgia for the Senate before polarization. When Biden was asked on Wednesday if he wanted to apologize, he refused.

Many have objected to Biden’s casual linking of white supremacy with political civility, but he’s making a deeper connection than he may understand. As I discuss in my book “The Polarizers: Postwar Architects of Our Partisan Era,” Congress was more civil back then as a direct result of a 20th-century party system organized around Jim Crow. Contrary to Biden’s argument, it is impossible to separate the courtesies from the racist politics that made them possible.

The Senate was different back then

The Senate that Biden entered after his first electoral victory in 1972 really was a different world from today’s chamber. By all quantitative measures, party membership was much less closely related to votes for bills. Voters, too, were less partisan. The year 1972 proved to be the 20th-century high-water mark for rates of split-ticket voting, in which voters chose one party’s candidate for congressional office and the other’s for the presidency. In 2016, by contrast, not a single state in the country saw a Senate candidate of one party and the presidential candidate of the other win the popular vote.

Did senators work across the aisle more because they were nicer to each other? More plausibly, the civility was an effect rather than a cause of the bipartisanship. What drove depolarization were interests, ideology and coalitional incentives based on the highly uncivil social arrangements of the Jim Crow South.

The South’s congressional delegation had become solidly Democratic after the violent defeat of Reconstruction in the late 19th century. This had nothing to do with support for New Deal-style liberalism and everything to do with suppressing partisan competition in the region, so that politicians would not seek to mobilize black support and thus jeopardize white supremacy. By the middle of the 20th century, Southern Democrats behaved as a bloc on policy questions relating to race and civil rights (and also, to a significant extent, labor law), while varying widely from right to left on questions of economic regulation and the welfare state. As it happens, Eastland was an arch-conservative across the board, voting against Medicare and the Elementary and Secondary Education Act in 1965.

This is where the norms of civility came from

After the New Deal, the Southern faction of Democrats frequently allied with Republicans in a “conservative coalition” to block liberal legislation. Their perches at the head of committees and subcommittees, thanks to seniority, aided their efforts. One study by House liberals found that more than a third of all Democratic committee and subcommittee chairmen voted more often against than with the majority of their own party on major votes in 1967 and 1968. Liberal Democrats, for their part, sometimes allied with moderate and liberal Republicans to pursue initiatives, most notably on civil rights. Ideological and policy divisions, in other words, cut across the party divide, so that ad hoc bipartisan coalitions were the main way to get things done.

This reinforced a set of cultural norms in Congress that focused on collegiality, decorum and disagreeing without being disagreeable. The culture that Biden celebrates in his recollections involved cloakroom folkways and booze-soaked bonhomie that were heavily shaped by Southern male members. (In his memoir, Walter Mondale recalls getting to know the Southern bulls through socializing in a Senate office hideaway that “always seemed to have a supply of excellent bourbon.”) Southerners enjoyed long tenures representing one-party districts and states and mastered, like few others, the art of fluid bipartisan coalition-making as a tool for securing their interests. A powerful set of behavioral customs emerged as byproducts of these hard-nosed pursuits.

As civil rights emerged, these norms fell away

White supremacy drove the cross-party arrangements that fostered these customs. As white supremacy came under challenge, these arrangements unraveled. Civil rights became an increasingly central pillar of Northern Democrats’ political agenda, a process accelerated by the direct-action tactics of a mass movement on the ground. President Lyndon Johnson’s zealous advocacy of the 1964 Civil Rights Act and Republican presidential nominee Barry Goldwater’s opposition to it sent a signal about the parties’ emerging positions on racial questions, with long-term effects for presidential voting. Civil rights activists also contributed to a liberal Democratic reform agenda inside Congress that had by the mid-1970s challenged the sanctity of seniority and centralized power in party leaders. This was all intended to bring to heel the old Southern committee barons who had opposed civil rights and other liberal legislation.

Both Jim Crow and the power of its legislative defenders had begun to crumble by the time Biden arrived in the Senate, but it took years for the parties to reorganize themselves and for norms to disintegrate completely. Some Southern Democrats facing new challenges switched parties, others (such as Eastland) chose to retire, and others still moderated their legislative behavior to more closely match that of their co-partisans. During the years of flux, when Biden came of age in Congress, both chambers retained a good deal of the mid-century era’s characteristic bipartisanship and unpredictability. But the great sorting-out of the parties by ideology was underway.

Congress in 2019 is anything but politically fluid. Conservative Republicans enjoy a near-lock on non-majority-minority Southern states and districts. Racial politics, like so many other issues, now reinforce the party divide instead of cutting across it, and the parties have strong incentives to be antagonistic toward each other. All the Biden bull sessions in the world would do little to alter these basic features of politics. And since the era of boozy politesse in Congress was made possible by the basic denial of civil and political rights to African Americans in the South — not to mention the near-total absence of women from those chambers — that’s not entirely to be lamented.

Sam Rosenfeld (@sam_rosenfeld) is an assistant professor of political science at Colgate University and the author of The Polarizers: Postwar Architects of Our Partisan Era (University of Chicago Press, 2018).