In Georgia’s Senate runoff elections, Republicans are banking on a strategy that generations of segregationist politicians perfected: Array the voters in rural counties, overwhelmingly white and conservative, against those in the Atlanta area. From the Jim Crow era to our day, the antagonism between rural enclaves and greater Atlanta has shaped Georgia’s politics.

The Republican senators, David Perdue and Kelly Loeffler, have decided that the key is turning out their rural base. Yet the rapid growth of metropolitan Atlanta, combined with tireless efforts to protect African-Americans’ voting rights, has transformed the state’s political landscape.

Joe Biden’s victory in Georgia was especially meaningful not only because it upended decades-long trends in party politics but also because it represented a possible turning point in a much longer racial history. Mr. Biden is the first Democrat to carry Georgia since Bill Clinton in 1992. Mr. Clinton, though, won the state with only 43.5 percent of the vote, and he performed well among white voters in rural areas. Mr. Biden put together a very different political coalition — more urban and suburban, more multiracial and more progressive. It is this coalition that the Democratic Senate candidates, Jon Ossoff and the Rev. Raphael Warnock, are counting on.

Politicians in Jim Crow Georgia possessed a tool that Mr. Perdue and Ms. Loeffler would have envied: the county-unit system. The winner of each county received all of its unit votes. The eight largest counties had six unit votes apiece, 30 counties possessed four unit votes each, and the smallest 121 counties held two unit votes apiece. In 1950, Georgia’s three least-populous counties — with 9,267 total residents — combined for six unit votes, the same as Fulton County, with 473,572 residents. This system of malapportionment empowered demagogues, none more successful than Eugene Talmadge.

Wealthy executives bankrolled Talmadge’s numerous political campaigns, while many white farmers supplied the votes. (He served three terms as the state’s governor — two from 1933 to 1937 and one from 1941 to 1943.) Talmadge was a vocal opponent of the New Deal, yet he depended on the support of those impoverished Georgians who stood to benefit from many federal programs. The journalist Robert Sherrill, in his book “Gothic Politics in the Deep South,” explained why “the people” still stood by Talmadge: “Old Gene had never done anything for them, but he made them feel like people, fit for laughter, supreme over the black man at least, and sharing with him the sly knowledge that since only the rich could profit from government, the poor man was foolish to take government seriously.”

In many ways, Talmadge — though he was a Democrat and his party backed the social programs of the early New Deal — created a blueprint for today’s Republican Party. He combined racial animus with anti-government rhetoric, piled up votes among rural whites and exploited a system that gave those voters disproportionate power.