By tenaciously courting South Carolina's increasingly important black vote, Republican Sen. Strom Thurmond is a sight early favorite for reelection over Democrat Charles (Pug) Ravenel - causing Ravenel's operatives to dredge up Thurmond's old Dixiecrat rhetoric.

Thurmond has gently dulled his sharp conservative edge to run against the telegenic Ravenel; his American Conservative Union rating declined from 100 percent in 1976 to 82 percent last year. but his courting of South Carolina's balcks - who will be casting about 27 percent of the 1978 vote - does not rest on any ideological transformation. Rather, it rests on personal contact, a form of Old South politics that Thurmond, 75, has now proved he can play as well with balcks as with voters.

To counter that, the Revenel campaign points to harsh segregationist statements by Thurmond in 1948, when he carried four states against Harry Truman as presidential candidate of the States Rights Democratic Party (Dixecrat). But the past may not be able to obliterate the present. "No one, but no one, can deliver like the senator," one South Carolina black leader told us.

Thurmond's vestigial influence in the vast federal bureaucracy extends to regional offices in Atlanta still staffed with Republicans from the Nixon-ford era. That often gives him a unique advantage in announcing federal grants and bird-dogging federal projects of particular interest to black voters.

Thurmond's fstidious attention to black constituents he once spurned is aimed at at least doubling the 8 percent vote he achieved in 1972. White votes were plenty then for his 64 percent runaway third-term election.

No runaway is in prospect this year against Revenel, the 40-year-old Charleston blurblood who came from nowhere in 1974 to win the Democratic nomination for governor. Ravenel's brilliant use of television made him a cinch for election until he was forced off the ballot by a nonresidence technicality.

Thus, Thurmond's chances may turn on whether he can double or even triple that 8 percent black vote, a possibility that disturbs managers. Going back 30 years, they have constructed a record of anti-black, anti-civil rights statements by Thurmond that reads like a page from the South's Jim Crow past.

As Dixiecrat candidate in 1948, Thurmond said, "There are not enough troops in the Army to force southern people to admit Negroes into our theaters, swimming pools and homes." In 1965, after becoming a Republican, he attacked civil rights demonstrators as "communist led and inspired."

Although Ravenel told us he personally would have nothing to do withcirculating that record to black voting precincts, one campaign aide said it would be "available" to anyone who asks. However, Thurmond's ardous wooing of blacks the past seven years could cause an anti-Thurmond campaign to backfire against Ravenel.

"We don't care what the senator did in the '40s and '50s," Isaac [Ike] Williams, head of the state NAACP told us, "but how he is repsenting us in 1978." Williams, while uncommitted, said that if voters "just try to punish a politician for the sins of the past, what does it profit him to improve?"

Considering where he started, Thurmond's improvement is indisputable. He has established scholarships for balck students at four South Carolina colleges with religious affiliatons, nailing down political contacts that reach deep into the state's black Baptists and Methodists. In 1971, he became the first Deep South senator to put a black aide in charge of his home-state office, and now has seven balcks on his staff. (Sen. James Eastland [D-Miss.], running for reelection, just hired his first.)

There is also a convoluted racial factor that could help Thurmond by hurting Ravenel. After he was ruled out of the 1974 race for governor, Ravenel refused to endrose former Rep. William Jennings Bryan Dorn, his successor as Democratic nominee. Dorn narrowly lost to the present governor, Dr. James whose official trip to South Africa infuriated black voters. Unfairly or not, some of that anger is directed against Ravenel for helping elect Edwards by not helping Dorn.

More dangerous to Ravenel is Thurmond's valid claim of full credit for the expected nomination of Mattew Perry as the South's first black federal district judge. Perry is now a judge on the military Court of Appeals - also thanks to Thurmond's patronage.

Such actions, though large in symbolism, have little bread-and-butter meaning for the state's blacks. In today's politics, however, issues often lose force at the expense of imagery - a fact well known to canny old pol Strom Thurmond. Accordingly, the symbol of a reformed Thurmond aiding his black constituents may be more decisive in this year's election than the hackneysymbol of Time for a Change.