Of populism and Reagan coattails. Republican roots may not run too deep in the soil of the South

With his cotton gin running next door, Wynder Smith plants his dusty boots, tips back in his rocker, flips his bill cap on to the cement floor of his farm supply store, and becomes serious. Republican farm policies, he says, have meant ``disaster for the farmer.'' Just two years ago, Mr. Smith voted for Ronald Reagan. Now he's voting Democratic, for Wyche Fowler to replace Georgia's first GOP senator in modern times, Mack Mattingly. (Senate GOP freshmen, Page 16.)

``It's going back to rich folks and poor folks,'' he says. ``The Republicans aren't for the middle class.''

This is the old populist music that Democrats like Mr. Fowler, an Atlanta congressman, have so wanted to hear.

But it's faint music this year, in spite of a farm depression and foreign trade problems for rural industries. White working men like Smith have become the central battleground between the parties in the South. Black voters and white liberals are reliably Democratic. The suburbs are predominantly Republican. But the center of the South's political gravity is, as Atlanta pollster Claibourne Darden puts it, ``the fellow who lives in the country and drives a pickup truck with a rifle in the back.''

In this crucial United States Senate race, one of five in the South this year, Fowler fits slightly awkwardly with the very conservative country voter. As the saying goes, ``he's not from around here.'' Like the national Democratic candidates of recent decades -- with the half-hearted exception of Jimmy Carter -- the urban congressman is fighting the widespread conception that he is liberal.

Conservative Georgia Democrats with strong connections to county courthouses, such as Agricultural Commissioner Tommy Irvin and Georgia House Speaker Tom Murphy, are stumping zealously for Fowler. Fowler also benefits from a far more persuasive public presence than Mr. Mattingly. After the campaign's only debate this week, Fowler closed his distance from Mattingly in the polls by 10 percentage points.

Polls still show Mattingly comfortably ahead however, 48 to 40 percent in the latest WAGA-TV poll. Polls last month showed Fowler trailing specifically among rural voters.

The Democrats have another problem in Georgia. Mattingly drew standing ovations this week from groups like the Cobb County Young Realtors, blow-dried Atlanta suburbanites, who speak as often with the accents of Illinois, Michigan, or Pennsylvania as of Georgia.

``Wyche is a little too liberal for me,'' said one. ``He means well, but some of his ideas just cost too much money.''

Atlanta's suburban counties are among the fastest growing in the country. Cobb went roughly 70 percent for Mattingly in 1980, and it has 30 percent more registered voters now. Atlanta's metropolitan area already accounts for some 40 percent of Georgia's voters.

Still, elections in the South turn on which side can forge a coalition with the ``middle of the middle class,'' says pollster Darden, referring to his archetypal man in the pickup truck.

For all of their progress in recent years, Republicans have not set roots with these voters outside the mountain areas of the border south. County commissioners, district attorneys, and lieutenant governors continue overwhelmingly to be Democrats, even while Southerners vote consistently for Republican presidential nominees.

``Without roots [at the local level],'' says Darden of the GOP in the South, ``a tree can blow over in a small storm. . . . Until you start seeing Republican bumper stickers on old pickup trucks, you won't see a strong Republican realignment.''

Darden doesn't see even small storms this year in Georgia, however. Farmers like Wynder Smith are few, and for most workers this is a time of economic contentment, says Darden. In this environment, he sees Mattingly's incumbency as a crucial advantage.

Speaker Tom Murphy does not believe it. ``From every corner of every area in the state, my members tell me that Wyche can take their district,'' he says. Some suburbs of Atlanta and Augusta are Fowler's only weak areas, he insists.

Georgia representative Larry Walker, Democratic majority leader from middle Georgia, acknowledges that Fowler suffers from the liberal tag, ``that's poison in a state-wide race in Georgia,'' and that Mattingly has twice the campaign money Fowler has and has spent it on a torrential TV attack that has hurt Fowler.