With Orange County now blue, the last remaining Republican holdouts in California look pretty similar. Among their shared characteristics? Many were top destinations for Dust Bowl migrants of the 1930s.

So-called “Okies” and “Arkies,” sporting once-insulting nicknames that Okies later reclaimed as their own, fled the natural and man-made ecological disasters that swept through Oklahoma, Texas, Arkansas and Missouri during the farm crisis of the 1920s and the Great Depression that followed. They scattered throughout the nation. Hundreds of thousands ended up in California.

They made up a huge segment of the population in Central Valley counties such as Kern, Tulare and Madera. You can still hear their legacy in the country music known as the Bakersfield Sound and what researchers say are the remnants of Dust Bowl speech patterns. You can also see it in the area’s politics. Even after you account for its agrarian heritage, that part of the Central Valley remains more Republican than you’d expect.

You can thank the Dust Bowl for that, according to a new working paper from New York University Abu Dhabi political scientist Adam Ramey. Ramey found a strong relationship between the share of a county’s population that hailed from Dust Bowl states as of 1940 and support for Republican candidates in the 2018 midterms.

“No matter how I sliced it,” Ramey said, “I kept finding those results.”

There’s a popular misconception of those California migrants as windburned dirt farmers — think the cotton-growing Joad family of John Steinbeck’s “Grapes of Wrath” and Dorothea Lange’s famed photo of a migrant mother. But there were fewer farmers than you’d expect, according to a comprehensive analysis by Wheaton College economist Jason Long and his University of British Columbia colleague Henry Siu.

“If you actually look in the Census data from 1940 you find that agricultural employment is actually a low proportion of Okies,” Ramey said.

Instead, many of the migrants were white-collar and oil-and-gas workers, and they settled well beyond farming country. Bakersfield became a hot spot of Okie culture because of its oil wells, not because of its farms, Ramey said.

His analysis found little relationship between how rural or farm-heavy an area was in 1940 and how much of its population came from the Dust Bowl.

In keeping with methodology outlined in a 1989 publication by University of Washington historian James Gregory, who has long chronicled Dust Bowl migrants' lasting impact on the Golden State, Ramey used a broad definition of Dust Bowl, expanding beyond the region centered on the Texas and Oklahoma panhandles, to include all those who came to California in the 1920s and 1930s from Oklahoma, Arkansas, Texas and Missouri.

Gregory suggested Ramey expand his analysis by looking at Census counts of voting-age migrants from Oklahoma, Texas, Missouri and Arkansas each decade to account for California’s evolving population. At present, he told us, Ramey’s approach primarily shows the “San Joaquin Valley counties became and remained more conservative than the rest of the state.”

“When they first came, ‘Okie’ was a pejorative,” Ramey said. “Ultimately Okie became a badge of pride. Largely through music and cultural expression, they repurposed a negative word. It came to embrace not just those from Oklahoma, but all those people from the southwest plains region who were affected.”

The divide between urban and rural counties remains decisive in California, as it does in the nation as a whole. An area’s Dust Bowl heritage looms almost as large. Hispanic voters have displaced Okies as the largest group in many areas, yet Republicans have held on in counties with a strong Dust Bowl heritage even as they get “shellacked” in places like Orange County, Ramey said.

All else being equal, the share of the vote earned by Republican candidates fell almost a percentage point a year in the least Okie parts of California between 1980 and 2016.

In the places that accepted the most Okie refugees, the Republican share rose a few points over that time, Ramey found, even when other factors have been accounted for.

“As bad as it’s been for the Republicans in California? Without the Central Valley it would have been worse,” Ramey said. “The bottom really would have fallen out.”