Politics in the American South have shaped, and continue to shape, politics across the United States. The South’s profound political realignment after the passage of the Civil Rights Act in the 1960s helped the Republican Party contend for majority control of Congress, and the region became a stronghold for the party. Issues endemic in the South — such as the recent controversies about Confederate statues — reverberate well beyond the boundaries of the former Confederacy.

But what about the time before the civil rights movement and the ensuing realignment?

Paradoxically, the South was both a region apart and of central importance to national policy and politics. Its lawmakers were not only local representatives but ambassadors for the South itself. Writing in 1949, the renowned political scientist V.O. Key even wrote of how these men saw their task as managing the “ ‘foreign relations’ of the South with the rest of the nation.” Our new book, “Southern Nation: Congress and White Supremacy After Reconstruction” (Princeton University Press, 2018), sets out to understand how these foreign relations were conducted.

The book focuses on Southern congressional representatives in the crucial period between 1877 and 1932 — from when Reconstruction ended until the New Deal installed white Southerners in many important political positions in the country. At the time, the Democratic Party — which was the only vehicle for political influence in the South — was a national minority, and there was little prospect for a Southern politician being elected president.

At that time, Congress was where Southerners had at least some hope to obtain political power. In the words of one Southern Democrat, it was Congress — and the Senate in particular — “which has in the past, when all else failed, been the last refuge of the people of my beloved Southland when political passion and persecution sought to nullify their self-government.”

What “self-government” meant was unambiguous: the ability of the South’s white population to shape and sit atop the region’s racial hierarchy.

When Southern lawmakers arrived in Congress, they treated the maintenance of “self-government” and white supremacy as paramount. For this reason, they evaluated all legislation along two main dimensions: its direct consequences for public policy as well as its consequences, direct or indirect, for the racial order. If a piece of legislation had no implications for white supremacy, the South behaved as any other region: Its representatives had diverse preferences and were no more or less influential than their numbers would imply.

But when a policy threatened the region’s racial order, white Southern legislators’ intense support for this order enabled them to unify and then use bargaining or obstruction to change or derail the policy.

How could this Southern minority muster this power? Because legislators outside the South didn’t prioritize the civil and political rights of African Americans. It was a classic example of how intense factions can win when the majority is indifferent. Southern legislators cared a great deal more about preserving white supremacy than legislators from the rest of the country cared about democracy for all of the nation’s citizens.

One example was the momentous defeat of the Federal Elections Bill of 1891, which would have significantly altered U.S. federal elections and greatly limited the opportunity to disenfranchise African American voters. In both the House and Senate, a majority of lawmakers almost certainly supported the bill. President Benjamin Harrison did, too.

But key Republicans cared more about a different piece of financial legislation, which would increase the amount of currency in circulation. These Republicans secretly cut a deal with Southern representatives: They would help defeat the voting rights bill if Southerners supported the currency bill. That was enough to stop the last attempt to give real voting rights to blacks in the South for generations.

The Southern congressional minority’s intense commitment to white supremacy also affected their view of legislative rules. With Northern allies, they repeatedly helped write rules that would help them defend the South’s racial order. The most important of these were in the Senate. Until 1917, there was no rule that allowed majorities to end debate in the Senate, allowing minorities to use the filibuster to obstruct legislation. This was how Southerners helped block bills that would advance civil rights.

But with U.S. entry into World War I on the horizon, President Woodrow Wilson demanded a rule that would create “cloture,” or a means to end debate in the Senate.

A few Southerners believed that Northerners were no longer supportive of African American civil rights and argued that there was little “possibility of limited cloture being used by any majority . . . of northern Republicans to put the ignorant and incompetent negro over the white people of the South.” But they were the exception. Sen. Ellison “Cotton Ed” Smith (D-S.C.) warned that someday the North might again try to pass a civil rights bill “if a cloture rule is put in effect.”

So Southern Democrats helped draft a rule that would preserve their ability to block civil rights legislation. The rule required a two-thirds majority to end debate, ensuring that the South could defeat any proposal it opposed. In essence, the filibuster created an effective white Southern veto.

The South paid a huge price for its relentless commitment to white supremacy. Southerners regularly opposed bills that would benefit poor whites because they feared that blacks would benefit, too. One example was the Blair Bill, which would have significantly increased federal spending — largely in the South — to pay for primary education to fight illiteracy.

The proposal had wide support among whites and blacks in the South. Although majorities of Southern Democrats voted for it on several occasions, in the end, they balked. The reason was their fear that enhanced black literacy would undermine white supremacy. This hurt not only blacks but many white Southerners as well because the South’s underfunded education system hindered economic development in the region.

Because of its intense commitment to white supremacy, the Southern minority in Congress found many ways to increase its influence. But this leads to an important irony: Their efforts gave the South more political power but left the South much poorer.

David A. Bateman is an assistant professor at Cornell University and the author of “Disenfranchising Democracy: Constructing the Electorate in the United States, the United Kingdom, and France” (Cambridge University Press, 2018).  

Ira Katznelson is Ruggles Professor of Political Science and History at Columbia University and the author of “Fear Itself: The New Deal and the Origins of Our Time” (Liveright, 2013).

John S. Lapinski is the Robert A. Fox Professor of Political Science at the University of Pennsylvania and the author of “The Substance of Representation: Congress, American Political Development, and Lawmaking” (Princeton University Press, 2013).