After helping a little-known county prosecutor become Virginia's attorney general, G. Bryan Slater headed south in 1995 to help pump life into Georgia's Republican Party.

At 34, Slater was young to be executive director of a statewide political organization, but a year into the job he used the direct-mail tricks of an old campaign pro to defeat several Democratic legislators, picking up a record eight seats in the Georgia statehouse.

"We went after them and went after 'em hard," Slater said. "We caught 'em with their pants down in '96."

Slater has since returned here to serve as a Cabinet secretary for his prosecutor pal--now Gov. James S. Gilmore III--and Republicans hope to make similar conquests in the state tomorrow when all 140 seats in the very narrowly divided legislature are up for grabs.

But Slater's I-85 shuffle from one southern capital to another is part of the story of the Republicans' advance in Dixie.

From governorships to legislatures and courthouses, the GOP is on a march across the Old South, led by low-tax, law-and-order conservatives like Gilmore.

Republicans control the South Carolina House for the first time since the era of Reconstruction after the Civil War. Republicans took over Florida's legislature in 1996 and hold the governorship, as well. They have the Texas Senate. In Kentucky, two state senators switched parties, giving the GOP a 20 to 18 advantage.

Nationwide, Democrats now control 20 state legislatures and the GOP has 19, with 10 split between the two political parties. (Nebraska's legislature is nonpartisan.) For Republicans, 1994 was the banner year: They not only captured Congress but also won more statehouses than they had since 1968. In the South, the advancing line is not without some breaks: South Carolina unseated a Republican governor last year, and the Georgia General Assembly is still ruled by Democrats.

But "the states now are as competitive as they've ever been" politically, said Tim Storey, a Denver-based analyst for the National Conference of State Legislatures who tracks the partisan alignment in capitals across the country.

"People aren't just automatically registering Democratic," he said. "It's been slow for Republicans--fits and starts. But they're on a roll. They've done a good job of pushing their agenda."

The combination of conservatism, political savvy and aggressiveness that Slater illustrates has helped put both houses of the legislature of his native Virginia within reach of Republicans in tomorrow's election.

Virginia, once the capital of the Confederacy, was dominated for decades by the Democratic Party, as was the rest of the Old South. That power was broken only briefly during Reconstruction.

Virginia Republicans began their advance in the 1970s, but the party has a rich history bred in the hollows of the Shenandoah Valley, a place far removed from slaveholding Richmond and the state's Tidewater and Southside regions. Linwood Holton, the first modern Republican governor, elected in 1969, had a political base in Virginia's highlands, as did John N. Dalton, who was elected governor in 1977.

Gilmore, elected in 1997, and Republican George Allen, elected in 1993, struck a more partisan chord than their independent-minded predecessors, aiming specifically for rural and suburban voters on issues that included Allen's call for welfare reform and truth in prison sentencing as well as Gilmore's electoral silver bullet, the phased-in repeal of the property tax on cars and trucks.

"In a mid-Atlantic state, can our party capture complete control?" asked Tim Phillips, a South Carolina native who has struggled since the early 1980s to get Virginia Republicans elected. Virginia, he said, tells the South that "the answer is absolutely yes."

Storey and other experts see a gradual weakening of the hold that conservative Democrats have long enjoyed in the South, as suburban voters elect legislators and governors who tend to be sensitive to their pocketbook issues.

"The Republican Party is becoming the party of the suburbs. They call themselves Democratic but vote Republican," said Dick Leggitt, a Southern Maryland resident who has built a career overseeing the media operations of Sun Belt Republican campaigns.

Virginia's Democrats have not abandoned the fight. Like the Republicans, they are focusing on 12 competitive races for legislative seats, half of them in the Northern Virginia suburbs. Among the themes struck by Democrats in their campaigns: Improve public schools, hold health-maintenance organizations accountable, seek more money for roads and mass transit and fight for tougher gun-control measures.

Their polling suggests that the gun-control issue is particularly powerful among suburban voters, and they hope to make gains against Republican incumbents while holding on to several open seats formerly held by Democrats.

But on many of this year's key issues, such as solving transportation congestion, the two parties have developed similar-sounding proposals. Democrats and Republicans both pledge to spend several billion dollars on improving roads and transit.

Republicans already have a razor-thin majority in the Virginia Senate and are within striking distance of winning the House of Delegates. Four years ago, Allen campaigned in vain for a new GOP majority in the legislature. Gilmore has since taken up that cause with a passion, crisscrossing the state for more than a year and right through this weekend in search of votes.

Gilmore has been canny about creating openings for Republicans, enticing Democratic lawmakers from GOP-leaning districts to join his administration. And he has stuck steadfastly to the car tax cut program that won him the governorship.

"The tax issue is still resonating in that region," said Raymond C. Scheppach, executive director of the National Governors' Association. "There's kind of an anti-government attitude still in the South, a minimalist view."

David M. Beasley, a Democrat turned Republican who was South Carolina's governor for a term until last year, said the South's GOP consistently recruits attractive candidates with powerful messages.

"What's helped the Republican Party in the last 10 years has been good faces, like Gilmore's," Beasley said. "It's what I call gut-type perceptions. It's a message of less taxes, less government and more individual freedom--that's what resonates in the South."

Slater, now Gilmore's secretary of administration, said he was able to gain ground in the 1996 Georgia races with a deluge of mail, 1.2 million pieces of literature targeted to 34 legislative races.

But in the end, it was the GOP's message that made inroads into the Democratic majority, Slater said. "The Republican Party is more in touch with average, moderate-to-conservative voters throughout the South.

"People care about three things: their children, their wallet and their safety," he said.

Now, hoping with his longtime chum, the governor, to celebrate a Republican takeover of the Virginia legislature, Slater said, "We're on message on all three."

CAPTION: G. Bryan Slater has helped run GOP campaigns in Virginia and Georgia.