In 1961, the journalist John Bainbridge wrote that Texans were “Super-Americans,” exhibiting American traits in abundance—like other Americans, only more so. Miller is, in spite of himself, a classic American type: amiable, self-educated, able to tap baffling and sometimes unnerving reserves of confidence. Born in 1973 in Longview to a teen mother, he met his biological father, the son of Greek immigrants, as a teenager. His mother’s parents, both working-class and only modestly educated, raised him; he called them Mom and Dad. “Dad went to the ninth grade twice, and quit both times when football season was over,” he told me.

In his early teens, Miller became a pen pal of the ex-astronaut John Glenn, who was then a U.S. senator from Ohio. At the age of 18, when Miller decided to run for mayor of his hometown on a sober platform of economic diversification, Glenn connected him with Senator Lloyd Bentsen, whose staff gave Miller advice on political campaigning. (He lost.) Miller attended college without taking a degree. He loads his conversation with references to political and cultural figures. His grandparents wanted an intellectual life for him, he said. “I read like nuts.”

Tragedy struck the family, Miller said, courtesy of the federal government. His grandfather, an ironworker and a Korean War vet, had shortchanged the IRS in what Miller said was an honest mistake. The old man spent the last years of his life fighting with the Department of Veterans Affairs while saddled with a tax-payment plan whose last installment came due just as he was ready to die. In reading the Constitution, Miller found plenty of limited-government wisdom, but none of the justification for what he saw as a behemoth of a state, one he believed persecuted his grandfather. “I saw how incongruent America was with what we believed America was,” he said. “It was like we went to Jack in the Box, ordered a hamburger, and got a sack of tacos.”

For a period of time, Miller voted angrily for anyone, of any party, willing to fight against the federal government. But then he hit on a wilder remedy: What if there were no federal government at all? He joined a small but hardy band of secessionists in 1996. “I set out on a journey that would consume much of my adult life,” he later wrote in a manifesto. Normally jovial, his face grew solemn as he described his conversion. “I decided: I’m going to do this. And I’m going to do this until it’s done.”

Independence movements have been rising and falling in Texas ever since it became a state. When Texas joined the union, in 1845, it had spent nine years as its own country, following its defeat of Mexico in one of a series of underdog victories by revolutionary movements in the Atlantic. But it was a start-up country, never more than a few months ahead of bankruptcy. Mexico had begun raids into Texas territory, and Mexican irredentism was growing. Texas joined the United States for the same reason Latvia, having left the Soviet Union in 1991, joined NATO in 2004: It worried that without a security guarantee, it would be absorbed back into the polity from which it had just secured its freedom.