METAIRIE, La. — The crucial cultural dividing line in Louisiana has always been north-south. Those who live in north Louisiana are mostly Protestant, speak with a familiar Southern twang and, in the modern era, voted heavily Republican. But rural South Louisiana is more Catholic, the accent is like nothing else (as anyone knows listening to the L.S.U. football coach Ed Orgeron on Saturdays) and the politics has tended more Democratic.

“If you looked around and saw oak trees and Spanish moss, you knew you were in a Democratic and Catholic part of the state,” said Trey Ourso, a Democratic strategist, recounting an old rule of thumb. “If you saw pine trees, you were in a more Protestant and Republican area.”

Yet as Louisiana voters go to the polls Saturday to decide the highly competitive runoff for governor between Gov. John Bel Edwards, a Democrat, and Eddie Rispone, his Republican challenger, the traditional regional divide is giving way to an urban versus rural political chasm that is shaping elections across the country. Republicans are dominating the countryside across much of the state, while Democrats are running up large margins in the cities in both the north and south while gaining strength in the suburbs.

Mr. Edwards, a pro-gun, anti-abortion-rights native of a small town, has spent much of his time in Louisiana’s cities as the campaign wound down. He appeared in New Orleans earlier in the week at a black-owned art studio, filled with a mix of respectful and creative renderings of Fannie Lou Hamer, Malcolm X and J. Edgar Hoover, and returned to the city Friday for a concert featuring the local music legend Trombone Shorty.