WHEN Southern voters head for the polls this November, a growing number of them will vote Republican. A few decades ago, this would have been an act of heresy in the Dixiecrat South, long a bastion of conservative Democrats.
From Florida to Texas, the region's cadre in the United States Congress has become increasingly Republican, and Republican pollsters and political analysts predict the time may not be far off - perhaps this election year or in 1996 - when the GOP can claim the region as its new powerbase.
``The changing composition of the region's congressional delegation is one of the most important stories in US politics,'' acknowledges Merle Black, a political science professor at Emory University in Atlanta.
A shift in the regional makeup of the GOP has been reflected in the US House of Representatives between 1968 and 1992, says Steve Lombardo, a Republican pollster with Marketing Strategies, Inc., in Washington, D.C. who tracked the numbers this summer with his partner Alex Gage.
During those years, the GOP's traditional powerbase in the Midwest eroded and the Midwest itself lost a number of congressional seats.
While the party controlled 79 of the Midwest's 125 congressional House seats in 1968, today only 44 Republicans hold the region's 105 seats. In 1968, 41 percent of the Republican caucus came from the Midwest; today only 25 percent does.
The South, meanwhile, has increased its Republican ranks from 35 members in 1968 to 56 in 1992. Mr. Lombardo and Mr. Gage divide the South into two mini-regions: the Deep South - Texas, Arkansas, Mississippi, Alabama, Georgia, Florida, North Carolina, South Carolina, Louisiana, and Virginia - and the border South, an area they define as encompassing Oklahoma, West Virginia, Tennessee, Kentucky, Maryland, and Delaware.
Although a growing population and congressional reapportionment in the South have boosted the number of the region's House seats from 132 to 148, Lombardo maintains that the gradual addition of 21 GOP-held seats - all in the 10 states of the Deep South - is a dramatic 100 percent increase for the Republicans. Today, 32 percent of all Republican House members come from the South versus 19 percent in 1968.
In other regions, the GOP has either lost seats (Mid-Atlantic, New England) or gained just a few seats since 1968 (the Mountain States and the West).
Republicans are still a ways from being able to claim the South as their powerbase - a region where a political party wins a large majority of the congressional contests most of the time.
``We still have a minority of seats in the South,'' Lombardo says. ``But we may get close to reaching majority in the South in '94, and if the growth that a lot of people are talking about occurs - a major GOP surge - it could mean a revolutionary change.''
Southern Republicans are giddy about their prospects in the South this year, and pundits predict they could capture anywhere from eight to 12 seats. In 1992, they gained nine seats in the South.
A big Republican win next month, combined with conservative Southern Democrats who may switch parties for plum committee assignments, could give the GOP the 40 more seats they need to control the House for the first time since 1954.
The growth of Republicans in the South is ``a very serious phenomenon for Democrats, and one which is probably going to cost us a number of seats,'' concedes Mark Mellman, a Democratic pollster and president of Mellman, Lazarus, Lake in Washington. ``A lot of the open seats this year are in the South and border states in areas that are difficult for us to capture, in a year that's difficult for us to capture.''
The South is turning out a different kind of Republican, Lombardo says. ``Whereas the Midwest would produce what we would call more progressive Republicans, the Southern Republicans are much more conservative in terms of ideology.''
In addition, the South is seeing the growing clout of what Mr. Black calls migrants - such as Republican Whip Newt Gingrich of Georgia, and Richard Armey of Texas, who will hold the No. 2 Republican leadership position next year - who were not raised in the South.
``Their style does well in Southern suburbs and represents the values of the increasing middle-class South,'' Black says. ``Their influence is just beginning.''
Blease Graham, a political science professor at the University of South Carolina in Columbia, agrees and points to a trend he sees, namely the transition of long-established Democratic districts into Republican ones.
``What that means is that instead of having a small-town social and fiscal conservative who was the Democrat, now [you have a Republican] who combines economic libert-arianism and a less tolerant social conservatism,'' he says.
But Mr. Mellman says the shift toward a more conservative Republican Party helps Democrats.
``A lot of southern Republican candidates are from the extreme right,'' he says, ``and it is the extreme right which repels many Americans and pushes them right back into the arms of the Democratic Party.''