Born in 1916 in northern Mexico into a poverty-stricken family that crossed the border when he was a child, Mr. Castro was elected Arizona’s first and only Latino governor in 1974, the pinnacle of an exceptional political career that seems nearly unimaginable to replicate in today’s Arizona.

Since Mr. Castro’s historic victory 46 years ago, no Latino has been elected to any statewide office in Arizona, much less as governor. Instead, Arizona turned into a testing ground for policies aimed at keeping foreigners out and curbing the influence of Latinos in American politics — policies that helped lay the groundwork for anti-immigrant measures in other states and in the Trump White House.

Ten years ago this spring, Arizona’s leaders enacted one of the most contentious anti-immigration bills that any state has adopted in recent history: SB 1070, the first of the so-called “show me your papers” laws, which gave Sheriff Joe Arpaio of Maricopa County and other local police officers broad power to detain anyone without a warrant if they suspected they had committed a deportable offense.

The state also required employers to screen out undocumented workers, disqualified undocumented immigrants from in-state tuition rates, and introduced barriers making it harder for Latinos to vote. Even now, states around the country are implementing laws that mirror Arizona’s earlier attempts to limit immigration.

But as voters head to the polls for the state’s Democratic primary on Tuesday, the tangled politics of immigration in Arizona have become more unpredictable, and even some Republicans and independents in the state are rejecting the divisive politics of the past 20 years — suggesting that President Trump’s hard-line immigration policies may not find the widespread approval in Arizona they once might have.

Just how far the pendulum has swung became clear earlier this year, when the Republican governor, Doug Ducey, proposed a constitutional amendment to enshrine a ban on sanctuary cities — a measure that only a few years ago might have won easy approval. Clearly, Mr. Ducey expected that it still might.

But hearings on the issue in the state legislature erupted into chaos, amid an outcry from Latino leaders and immigrant advocates. The state’s business community sent an immediate signal of alarm to the governor. Soon after he proposed the measure, the governor withdrew it.

“Ducey overplayed his hand,” said Isela Blanc, 48, a former undocumented immigrant who won election to Arizona’s House of Representatives in 2016. “This isn’t the same Arizona as in 2010. There’s little appetite for reliving that nightmare again.”

The story of Arizona’s turbulent evolution on immigration — from Raúl Castro to Joe Arpaio to the election in 2018 of Kyrsten Sinema, a Democrat, to the U.S. Senate — provides a fascinating lesson in the history of the Southwest and, possibly, the future of the Democratic Party as it challenges Republican supremacy in traditional strongholds.