It is High Noon for Herman Talmadge, Georgia's cigar-chomping senator who spent today dialing desperately for dollars and votes, calling in the chits he has built up by performing favors during four terms in Washington.

For the first time in his long political career, Talmadge faces a runoff, and has but three short weeks to make what could be his last stand against a fiery populist, Lt. Gov. Zell Miller, the man who would be Kingfish.

Should Talmadge survive the Aug. 26 runoff, it would be testimony to his political caginess, his survivability. "If he pulls it out of the fire, it will be the greatest political resurrection of all time," said a long-time supporter last night.

Georgia history teaches that a powerful incumbent forced into a runoff is a dead politician.

Should Talmadge lose, his passing would mean the loss of yet another of Dixie's most endangered species, the Gothic southern politician, further ushering in pronouncements of the New, New, New, New South.

He pulled a disappointing 40 percent of the vote in a six-man field in Tuesday's bloody Democratic primary, down from a July poll that gave him 48 percent.

Miller, 48, fought his way into the runoff with 25 percent. A college history professor, Miller has cultivated an intellectual hillbilly image replete with cowboy boots, a Stetson hat and a penchant for listening to Kris Kristofferson's "To Beat the Devil" on the tape deck of his van. The lieutenant governor has form into Talmadge with a stridency that has made the old guard wince.

A perceived liberal, Miller, will certainly have to expand his coalition of big labor, blacks, the education establishment and the Volvo station wagon and Brie set if he is to beat up on Talmadge in the runoff. Miller's slogan: The Best Senator Money Can't Buy.

To unseat a legend, Miller will have to broaden his base and shake off the liberal image. He must capture most of the voters who cast their ballots Tuesday for the two most conservative candidates in the race, former appeals court judge Norman Underwood, who pulled in 20 percent, and Rep. Dawson Mathis, who garnered 12 percent.

For 24 years, Talmadge, 67 -- seventh ranking senator, fifth ranking Democrat, chairman of the Agriculture Committee, vice chairman of the Finance Committee -- has been a political institution, one of the most powerful men in the Senate, courted by colleagues in Washington, his seat unchallenged at home.

"The only real question over the past 30 years was whether I was going to get 69 percent or 81 percent," he has been telling his loyal dirt farmers on the stump and his big business establishment backers in their boardrooms. "But this year, it's gonna be different. I've got a rough race this time."

Indeed, late Tuesday night they saw how "different" it would be, as the band struck up "Happy Days Are Here Again" and the vote rolled into the downtown Hilton's grand ballroom. Many stauch supporters, anticipating victory without a runoff, appeared stunned.

Eyes glazed over in disbelief among the crowd sporting plastic Talmadge straw hats and red suspenders -- Depression Era fashion flashbacks to "Hummun's" gallus-thumping Daddy, Eugene, who launched the dynasty 50 years ago as governor. His slogan: "The poor dirt farmer ain't got but three friends on this earth -- God Almighty, Sears Roebuck and Gene Talmadge."

His boy Herman, reformed alcoholic, sipped lustily from a tumbler of H-2-O on the rocks and, surrounded by his five grandchildren, exhorted the faithful: "Get on your fighting clothes," He had warned them. They should have known.

For almost a year, opponents had been harping on his troubles. In 1975, his son drowned. In 1977, he divorced his wife, Betty. Last year, a victim of Scotch whiskey, he took the cure.

But perhaps Talmadge's greatest political misfortune, the Achilles heel opponents have hammered on, was the Senate denunciation in October 1979 for his failure to account for some $40,000 in office expense money. Senate colleagues termed his conduct "reprehensible" behavior that brought "dishonor" upon the Senate. One of his former aides went to jail for the purloined expenses.

The Justice Department, however, determined there was insufficient evidence to bring criminal charges against the senator.

In his darkest days last August, with the investigation of his expenses in high gear, his drinking finally under control, the divorce papers barely dry, the politicians smelled blood in the water and started circling the senator.

Miller was the first to move, biting into Talmadge for bringing "shame and dishonor to his state." He railed on the stump about "drunks rich enough to pay $250 a day to take the cure" and a "U.S. senator whose name is a household word in Georgia for making big land deals, hiding titles and profits in his wife's name, and overdrawing his expense account."

Another opponent fueled the fire with an anti-Talmadge TV ad showing money changing hands, including a shot of $100 bills stuffed in an overcoat, an allusion to Betty Talmadge's Senate testimony about his curious way of keeping pocket change around the house.

"We have a lot of senators who go down as profiles in courage," Miller carps. "We're going to have a senior senator from Georgia go down as a profile in cash."

Talmadge denies it, while opponents dare him to make his tax returns public. He has refused.

Miller denies that he has dirtied the race. "I haven't slung mud," he said."I've flung truth -- and it splattered all over this state."

Indeed, Herman Talmadge seems to be the issue.

But the senator has struck back, outspending his campaign opponents with a $1 million war chest that will surely swell over the next three weeks, and slick, bedazzling TV advertising that seeks to neutralize the negativity. In one ad, the senator solemnly professes, "The last five years of my life have been difficult. My youngest son died. I suffered an unfortunate divorce. My most trusted aide turned out to be an embezzler."

"None of my opponents has ever said anything kind about me," Talmadge reminds reporters over and over. "I'm sure they blame me for this heat wave and the volcanic eruptions in the state of Washington."

Talmadge has been stumping the state hard, showing remarkable stamina, puffing on his omnipresent cigar.

He has holed up in motel rooms across the state, dispensing favors to consistuents, dwelling on the benefits of his accrued power, reminding everyone of what he has done for them, what he can do. And all the while he warns them against allowing some young whippersnapper to take his job and their security away. A newcomer, he says, "wouldn't be able to find his way to the bathroom" for months.

He preaches a fire and brimstone Gospel of fear. "We're in extremis," he booms. "Neither you thought, nor I thought, that we'd see the day when the interest rate was 20 percent. That was something we thought Mafia loan sharks charged for money. Or 20 percent inflation. That was something that belonged to the banana republics of South America. Now the Soviet Union's Army is about twice the size of ours. But we're about to do something about that. If we don't, we'll reap the whirlwind."

He has even courted the black vote with a vigor unknown for a Talmadge. Once an arch-segregationist, he is lining up endorsements from black business leaders and preachers throughout the state, endorsements Miller has fought to deny him. The black vote represents 26 percent of Georgia's 1.4 million registered voters, but the mixed messages they have been receiving from various black leaders seem bound to confuse them, and may deny either candidate decisive black support.

Miller counts staunch allies in state Sen. Julian Bond and Atlanta Mayor Maynard Jackson, who has tried to move blacks into the Miller camp by equating a black vote for Herman Talmadge with spitting on the grave of Martin Luther King Jr.

Miller has emphasized Talmadge's history as a segregationist, and Talmadge has responded by vowing to vote to extend the civil rights voting law when it comes up in the Senate in 1982.

On Sunday Talmadge donned a blue suit and climbed the red velvet stage of downtown Atlanta's Wheat Street Baptish Church, delivering a knee-slapping sermon on forgiveness that elicited "amens" from the black multitude, "I've been accused of being a segregationist 25 years ago," he preached. "It's true. Do you know any white folks in Georgia who weren't segregationists 25 years ago?"

"NO!" shouted the multitude. He compared himself to "Saul on the road to Damascus," assuring them that a man can change. "It is by pardoning that we are pardoned." And then he launched into a laundry list of everything he had done for them: supporting food stamps for the needy, not the "leeches"; pushing the food lunch program so their children wouldn't go home hungry; urging the appointment of a black federal judge. Each claim evoked more amens and applause and he punctuated each with, "You can thank Herman Talmadge for that."