ATLANTA -- For months, Massachusetts Gov. Michael S. Dukakis has been quietly pouring money and manpower into four key southern states in preparation for the tidal wave of primaries on March 8, testing the ability of a liberal-leaning politician from the Northeast to pull votes in this key region of the nation.

"Dukakis has been walking on water in New Hampshire," said a southern Democratic strategist, referring to Dukakis' expected easy win in the state bordering his own. "Starting Wednesday, we'll see if he can walk through the tall cotton."

For Dukakis, Super Tuesday will not only provide a gauge of his strength in this gold mine of electoral votes, but it will also test the mood of an electorate that has given victories to such conservatives as Ronald Reagan and Sen. Jesse Helms (R-N.C.) and to such moderate-to-liberal Democrats as Sen. Wyche Fowler Jr. (Ga.) and Gov. Bill Clinton (Ark.).

To clear the path toward this major hurdle, Dukakis has invested five times as much as any of his competitors and has dispatched a small battalion of roughly 70 staff people, most of them assigned to four states: Florida, Texas, North Carolina and Georgia. On Tuesday, he is scheduled to affirm his commitment to the South at rallies here and in Florida.

Each of these states has large urban areas -- Miami, Tampa-St. Petersburg, Atlanta, Raleigh-Durham, Austin, Houston, Dallas -- where Dukakis can find a core of support among liberal whites, retirees from the Northeast and suburban reformers.

"Dukakis is trying to work a 'liberal pocket' strategy," Bill Carrick, manager of Rep. Richard A. Gephardt's (D-Mo.) campaign, said. Initial, post-Iowa caucus polling in Texas suggests that Gephardt may, among the white candidates, prove to be a formidable competitor in the South. A poll last week in the Dallas Morning News showed that Gephardt has shot into first place with 27 percent -- up from 8 percent in October, Jesse L. Jackson fell from 26 percent to 15 percent, Dukakis rose from 8 percent to 14 percent, and the rest of the candidates fell below that. Sen. Albert Gore Jr. (D-Tenn.), who has focused on the South, remained at 6 percent.

Dukakis' targeted southern strategy is, in part, an attempt to duplicate in the South the kind of strong backing he has received in his home state. In Massachusetts, Dukakis' strength has been far more reliable in the affluent Boston suburbs of Brookline and Newton than in the traditionally Democratic working class inner-city neighborhoods in South Boston and Lawrence. The Dukakis strategy is a reflection of how much the South has changed over the last 30 years.

Former South Carolina Democratic Party chairman Don Fowler, without referring to the Dukakis campaign directly, contends that the white portion of the southern Democratic constituency has, in fact, become very similar to that in Massachusetts and New York. Working-class voters in both areas have stopped participating in primary elections, Fowler says. This assessment, which is shared by North Carolina political scientist Merle Black, could well work to Dukakis' advantage.

Dukakis has, however, a long way to go before he gains full credibility in the Democratic South. Alabama State Sen. Mac Parsons, who has supported Gore, said: "Dukakis? I campaigned for Bill Baxley (the defeated Democratic gubernatorial nominee in Alabama). I campaigned for Mondale against Reagan. Hell, I'm tired of campaigning for unpopular people."

An essential element of Dukakis' strategy in the South has been to use his fund-raising advantages to flood potentially sympathetic areas with operatives so as to establish beachheads in terrain where often the local leadership looks upon him as a candidate who cannot sell in a southern general election. Texas Democratic Party Chairman Bob Slagle, who has endorsed Gore, contends that at the moment southerners see Dukakis as "just another Northeastern liberal."

Here in Georgia, however, the organizational investment has produced a number of internal party victories that have won Dukakis grudging praise. At recent statewide precinct caucuses, Dukakis backers produced the largest number of delegates, encouraging at least one party leader, who had privately viewed Dukakis eight months ago as "the kiss of death," to now comment that "maybe Dukakis, with a lot of work, could do something down here."

Privately, a number of Dukakis strategists acknowledge that the key southern state for their campaign may prove to be Florida, where Dukakis currently leads in the polls and has a staff of 19.

Marcia Hale, who is directing the Dukakis southern program, downplayed any expectations that Dukakis will need to win a plurality in any state. "Our goal is winning delegates," she said. "Coming out of Florida with a large number of delegates is critical to us."