He was an obscure $35,000-a-year IBM typewriter salesman with Indiana roots, fresh-scrubbed and smiley-faced as a Ken doll, and so possessed with confidence and naivete he actually believed he could dethrone Senate power-broker Herman Talmadge.

No one took Mack Mattingly seriously. except the voters.

He was a Republican in a state where Democrat is king, state chairman over a measly 50,000 Republicans (out of 2.4 million registered voters). He had lost the only race he'd ever run before -- for Congress 14 years back.

Yet, as one of the Reagan revolutionaries who won Southern state after Southern state, he helped write another closing chapter on the Old South. Mattingly's narrow victory is more than just the story of a remarkable upset in a startling political year, it advances the saga of southerners shaking off a century-old inferiority complex to put bread-and-butter issues before regional pride and become more like the rest of the country.

Election eve, wire services and major networks proclaimed Talmadge the winner. "Talmadge Walks Away With It," declared an early edition of the Atlanta Constitution. Georgia's crusty, cigar chomping senator had a cozy 55-to-45 lead. The dauphin to a powerful 50-year family political dynasty destined for a fifth term. His denunciation by Senate colleagues for financial misconduct, his bitter divorce, his drinking problem were all apparently forgotten.

But some time before the sun rose over Georgia Nov. 5 a gigantic suburban vote from around atlanta and other major cities came rolling in. Joinng the suburbanites were other elements of a classic New South urban coalition: Yankee emigres, Republicans, Talmadgehaters, some blacks and some young people -- all of them unswayed by the Talmadge mystique of seniority and service. And Talmadge came up short by 26,000 votes out of a record of more than 1.6 million cast.

The election of Mattingly was partly the triumph of big cities. Mattingly took the areas once pilloried by Talmadge and his gallus-thumping daddy, "Old Gene," who scorned carrying "any counties with streetcar tracks." Both Talmadge and "Old Gene" placed their faith and electoral futures in the hands of farmers and "wool hat boys" from the red clay countryside. but a shift has taken place in Georgia and elsewhere in the South, and the power has moved from rural to urban areas, increasingly dooming legends like Talmadge.

If Talmadge, 67, chairman of the powerful Senate Agriculture Committee, vice chairman of the Finance Committee, a power broker in Washington, a political godfather back home, is the surprise casualty of the Republican renaissance, then Mattingly is the political Rocky of the year. The 49-year-old Brunswick, Ga., businessman, who resigned from IBM and sold his stock and a small office supply company to finance a race he began plotting three years back, is the first Republican senator from Georgia since Reconstruction.

Just how this happened is still being studied under political microscopes by shell-shocked Talmadge backers and joyfully delirious Mattingly supporters in Georgia.

"It's so hard to sort out," says Mattingly fund-raiser and friend Ben Slade, a Brunswick, Ga., bank president.

"The carpetbaggers done him [Talmadge] in," laughed Jack Spalding, a retired Atlanta newspaper editor, referring to Mattingly's 150,000 vote (64 percent) margin from five metropolitan counties around Atlanta.

Returns show Talmadge won 130 rural counties to Mattingly's suburban 29. In the old days of Georgia's now defunct county unit system, roughly akin to a state electoral college, that would have spelled victory for "Hummon."

Consider Cobb County, the fastest growing Atlanta suburb and home to thousands of transplanted "Yankees" from New York, Ohio and California who drive BMW's, play golf, root for the Falcons and toil as middle managers for firms sprouting about the perimeter highway. Turf of conservative Rep. Larry McDonald Cobb County gave Mattingly 70 percent of its vote.

Pilloried mercilessly in the Atlanta newspapers, Talmadge bitterly charged in an interview that the suburbs were "poisoned" by the press with "thought control worse than the Germans had under Hitler."

Still, there was more to Mattingly's victory than suburbanites. Mattingly cut into Talmadge's lock on rural farmers, distraught over sky-rocketing interest rates and the worse drought in Georgia history. His inroads were slight but unprecedented. Even a Talmade, with his agriculture connections, couldn't make it rain.

He also reaped about a third of the black vote, unheard of for a Republican in Georgia. Part of it was attributable to Atlanta Mayor Maynard Jackson's statements to his fellow blacks in the Democratic primary that a vote for Talmadge, a former segregationist, was the moral equivalent of "spitting on the grave of Martin Luther King Jr."

"Talmadge's defeat demonstrates that Afro-American voters cannot any longer be taken for granted in Georgia -- you cannot spit in our eye ant tell us it's raining," said Jackson.

Such exhortations, however, back-fired in the Democratic runoff and helped Talmadge portray his challenger, Lt. Gov. Zell Miller, as a Kennedyesque liberal with deficit spending dreams. Miller's shrill personal attacks against Talmadge over his denunciation by the Senate, his wheeling and dealing and his problems with Scotch, had a lingering half life of their own. People remembered. Mattingly didn't have to remind them.

The political fallout allowed Mattingly to conserve his meager cash, stake out the high road and stick to raising his visibility, advancing his image as a budget balancing, tax cutting pragmatist, and to flail Talmadge above the belt highly memorable Tv spots. The ads freeze-framed Talmadge, his mouth in gear, declaring 1980 his most productive year in the Senate, while a narrator hyped his high absentee record.

After fighting off five hungry Democrats in the primary, Talmadge, forced into a runoff, trounced Miller with 58 percent of the vote in the August 26 runoff. But he miscalculated his victory as a reprieve and returned to Washington. A Caddell poll gave him a 20-percentage-point lead a month before the election, said Talmadge. He ignored Mattingly's call to debate.

"That killed him," said Mari Egbert, Mattingly's 27-year-old campaign whiz kid. "He put himself in a box. There was no way he could come out and fight without looking like he was scared."

Waving a Bob Teeter poll that put him 11 points behind Talmadge with two months to go, Mattingly secured a crucial $227,000 infusion from the Republaican senatorial committee and mounted a half-million-dollar media attack. He ran a faultless campaign. Republican statesmen like Sen. Howard Baker of Tennessee and former president Ford waltzed through Georgia for him. Another poll showed Mattingly slightly ahead the week before the election.No one believed it.

But Talmadge appeared frightened. He'd spent most of a $2 million war chest before the runoff and had trouble raising money for the final round. So he stooped to scare tactics, likening Mattingly, who moved to Georgia after college and service in the Air Force 25 years ago, and his staff to "carpetbaggers" leading Sherman's army through Georgia. It didn't work. He implored his people to get out and vote. It sounded like a wolf cry. Few could imagine a Talmadge whipped by a Republican.