President George W. Bush waves with Democratic Sen. Zell Miller (D-Ga.) in 2004. (Jason Reed/Reuters)

Zell Miller, a two-term conservative Democratic governor of Georgia who led the charge for the state’s lottery-funded HOPE scholarships in the 1990s, which sent hundreds of thousands of Georgians to college, and then served more than four years as an unpredictable and newsmaking U.S. senator who criticized many in his own party, died March 23 at his home in Young Harris, Ga. He was 86.

Lori Geary, a spokeswoman for the Miller Institute Foundation, confirmed the death but did not disclose further details. Mr. Miller’s relatives announced last year that he had been diagnosed with Parkinson’s disease.

Mr. Miller entered the history books as the only person ever to deliver keynote addresses at both major political parties’ presidential nominating conventions. He was a man unswervingly loyal to his Georgia mountain roots who came to be seen as a traitor by many in his political family. Mr. Miller helped resuscitate Bill Clinton’s failing 1992 presidential campaign and ended up becoming one of the Republican Party’s most vocal supporters.

Like the Appalachian Mountains that dominated his North Georgia vistas, Mr. Miller rose improbably high and presented numerous faces to the world: The Polonius-quoting college professor who also wrote a country song with the down-home title “You Can’t Ration Nothing I Ain’t Done Without.”

A onetime expert marksman Marine, he later armed every Georgia newborn with a classical music CD. An unsuccessful 1980 Senate candidate dubbed “Zig Zag Zell,” he roared back to become the state’s most popular governor — only to see much of what he’d accomplished drowned out by the din of his late-life political drama.

In the end, nothing mattered so much to him as the beginning.

Mr. Miller at the Republican National Convention in 2004. (Dennis Brack/Bloomberg News)

“Coming from a single parent, not having a lot of money, no electricity until I was 7, no running water until I was in high school . . . I’m proud that out of that could come someone who could make it to the governor’s office,” Mr. Miller told the Atlanta Journal-Constitution in 2006. “How I got from where I came from is very important to me.”

Journalists who covered Mr. Miller for years — or even days — could practically recite the stories by heart, he told them so often, so effectively.

“I came home early to watch him speak on TV at the [1992] Democratic Convention in New York, and I predicted, ‘In the next 15 minutes, you’ll hear about his mother, the creek, about Uncle Hoyle,’ ” Miller biographer Richard Hyatt said.

That speech, delivered with more than a hint of Appalachian twang and just enough bygone-era stump-speaking fervor to make Madison Square Garden feel like the smallest, most uplifted mountain village, introduced Mr. Miller to a national audience. He turned his mouth on Clinton’s opponents, George H.W. Bush and Ross Perot, in rapid-fire succession — “so much for the millionaire, now on to the billionaire,” he joked at one point.

The reviews were killer. “The national debut of Georgia Gov. Zell Miller was an evocative stemwinder in the best Democratic tradition,” Newsday raved in an editorial.

Twelve years later, he was back in Madison Square Garden, back making headlines. Mr. Miller was a U.S. senator and still a Democrat when he offered his high-profile support to President George W. Bush’s reelection bid in a speech at the Republican National Convention.

He’d already described the Democrats as being woefully out-of-step with an increasingly conservative, post-9/11 America in his 2003 book, “A National Party No More: The Conscience of a Conservative Democrat.” Now Mr. Miller accused them of having a “manic obsession” to bring down Bush. His own party’s nominee, Vietnam War veteran John F. Kerry, was “more wrong, more weak and more wobbly than any other national figure” on national security.

The speech caused a sensation, especially when Mr. Miller went on MSNBC afterward and angrily raised the possibility of challenging interviewer Chris Matthews to a duel.

Zell Bryan Miller was born in the village of Young Harris on Feb. 24, 1932. His father, Stephen, met his future wife, the former Birdie Bryan, while both were teaching at Young Harris College; he’d risen to the position of dean and served a term in the state Senate when, 17 days after the birth of his only son, he died of cerebral meningitis.

Left alone to raise an infant and 6-year-old daughter, Birdie Miller spent weeks hauling rocks out of a creek to build the Miller family home on a plot of land near the college campus. She served on the city council for a quarter-century, and Young Harris’s residents stopped by the rock house to chew over issues or pay their taxes.

An academic and debate star at Young Harris College, Mr. Miller won a partial scholarship to Emory University in Atlanta. But he felt backward and out-of-place on the cosmopolitan city campus, and after spending a night in the drunk tank, the 21-year-old dropout enlisted in the Marines. After three years, he enrolled at the University of Georgia, where he received a bachelor’s degree in political science in 1957 and a master’s degree in history in 1958.

In 1954, he married Shirley Carver, and they had two children. A complete list of survivors was not immediately available.

He was a professor at Young Harris College before winning a seat in the state Senate in 1960. He later worked for segregationist Gov. Lester Maddox (as his executive secretary) and Gov. Jimmy Carter (who appointed him to the State Board of Pardons and Paroles). He ran for Congress twice and lost, and tried unsuccessfully to topple Herman Talmadge in a brutal 1980 Democratic Senate primary. He was elected lieutenant governor four consecutive times, governor twice.

He was both ahead of his time and disappointingly of the times on race. Three years after opposing a school segregation bill on the floor of the state Senate in 1961, he spoke out against the federal Civil Rights Bill during his unsuccessful 1964 Democratic primary campaign for a seat in Congress. (“My words and actions have tormented me ever since,” Mr. Miller wrote in “A National Party No More.”)

He gambled his political fortunes on the idea of a state lottery deep in the heart of the conservative Bible Belt and was elected governor in 1990. He tried to remove the Confederate battle emblem from the state flag in the heart of Civil War country and was nearly run out of office in 1994.

Mr. Miller left the governor’s office in January 1999 with an 85 percent approval rating. The next year, Gov. Roy Barnes (D) asked Mr. Miller to go to Washington and fill the void left by the death of Sen. Paul Coverdell (R). Before going to Washington, Mr. Miller announced he wouldn’t “play the partisan game.” One of his first acts was to co-sponsor Bush’s tax cut bill with Sen. Phil Gramm (R-Tex.).

He lost some friends near the end of his political career, he reflected in 2006, but he claimed to have found something like inner peace.

“Churchill once said that history was going to be kind to him because he was going to write it,” Mr. Miller said. “I’ve tried to do a little of that, but I don’t worry about it. I’m content to let what happened speak for itself.”