Georgia Governor's Race Reveals Old South's Shifting Tide. ANALYSIS

GEORGIA'S 1990 gubernatorial race will provide a crucial test of the turbulent political waters running through the New South and could signal a new political era for the state. With its shifting demographics and voting patterns, Georgia faces potential changes that would have surprised both Civil War Gen. William Tecumseh Sherman and author Margaret Mitchell.

As the last state to return to the Union, Georgia has been the Old South's last bastion and a stronghold of conservative Democrats for more than 100 years. But the election 18 months away could bring dramatic changes that include:

Election of the state's first black governor.

Election of the state's first Republican governor since Reconstruction, boosting GOP visibility and power.

A shift in the state's political power base, from traditional ``good ol' boy voters'' and rural Georgia, to metropolitan Atlanta-area precincts.

All of Georgia's neighboring states, except Tennessee, now have Republican governors. Georgia, however, has not had a Republican governor since Rufus Bullock, an Augusta businessman born and raised in New York, was elected during Reconstruction. Georgia has never had a serious black contender in the gubernatorial race.

Historically, Georgia has elected governors from rural areas or small towns. Candidates have usually come out of the General Assembly, the legislative training ground that also provides most of them with a stamp of approval from the entrenched good-ol'-boy network.

Observers note, however, that the power of the ``rubber-stamp Democrats'' is declining. Voters are looking for a new style of governor and more openness in the Statehouse; they are tired of the closed-door politics.

With increasing numbers of new people pouring into the metropolitan Atlanta area and nearby counties, Georgia's demographics are changing fast. Many incoming voters are educated professionals with no associations with the ``War of Northern Aggression,'' or the politics of white supremacy.

Many of the surrounding counties that make up the area known as the ``donut'' along the city's beltline highway, have elected local Republicans. Some believe rising Republican strength in the metro area puts the GOP in the best position ever to capture the Statehouse. So far, though, Republicans have not had much grass-roots support among the state's 159 counties. Only one Republican, state Rep. Johnny Isakson, minority leader of the House, has entered the gubernatorial race so far.

Bill Shipp, former associate editor of the Atlanta Journal-Constitution and longtime political analyst, says he believes the suburban vote will elect the next governor. ``The real battle will be for the donut vote,'' Mr. Shipp says. Even former Gov. Lester Maddox, once the champion of rural voters, admits the rural vote no longer controls the gubernatorial race.

While Democratic Lt. Gov. Zell Miller is the only candidate officially to announce his gubernatorial bid, the slate is expected to include a half dozen other names. Claibourne Darden, of Darden Research Corporation, Georgia's leading public opinion service, identifies four leading candidates - all Democratic - that include: state Sen. Roy Barnes; Lieutenant Governor Miller; state Rep. Lauren (Bubba) McDonald; and Andrew Young, Atlanta's mayor and President Carter's UN ambassador.

Though Mr. Darden has not yet polled voters about Georgia's gubernatorial primaries, he and other observers label Miller, one of the longest-serving lieutenant governors in the country, the pre-race favorite.

Though the race is still 18 months away, Miller has a well-organized campaign already in place and has raised more than $1.3 million in funds. Unlike other candidates, he boasts a political base both broad and deep.

Mr. Young, Atlanta's second-term mayor and the first black representative in the Fifth District (the area that includes most of Atlanta), is a formidable contender. A supersalesman for the city, he has promoted economic development and won support from business and blacks.

But the former aide to Martin Luther King Jr. may not get solid support from Atlanta's 70 percent black population. Some observers feel he is perceived as anti-neighborhood because he has not made enough progress improving inner-city housing and public services. Viewed as a liberal and Wall Street type by many around the state, Young is also unlikely to get many rural votes.