The Democratic sweep yesterday marks a significant shift in perceptions of Virginia, both outside the state and at home, political scientists and party strategists said. The outcome upset earlier predictions that the ticket would be doomed by the presence of a black candidate for lieutenant governor and a woman running for attorney general.

It also showed that the Democrats could effectively blunt traditional Republican attempts to paint their rivals as big spenders -- a task made difficult, politicians and strategists of both parties said, by the popularity and record of Gov. Charles S. Robb, a fiscal conservative.

"Republicans this time didn't have the scare tactics they could use in the past," said J. Marshall Coleman, Robb's Republican opponent in 1981. "It was no longer credible to say that if the Democrats win, it would be the end of the Virginian way of life."

The victories by L. Douglas Wilder for lieutenant governor and Mary Sue Terry for attorney general are "very significant for Robb," said Bob Roberts, assistant professor of political science at James Madison University in Harrisonburg, Va. "It gives him national credibility. It shows that he has coattails."

The outcome also indicated that "we are slowly entering the post-Reagan era in politics," said Democratic strategist Robert Shrum. The ticket headed by moderate Gerald L. Baliles "passed the fiscal litmus test that Democrats have to pass to get elected. It shows you can be progressive on all issues if you don't spend and spend and spend."

Both Wilder and Terry were credited by political experts with running campaigns that downplayed sex and race and portrayed them as moderate, mainstream, seasoned lawmakers.

It's a "tremendous breakthrough," said Merle Black, a political science professor at the University of North Carolina, describing Wilder's successful effort to become the first black in the South since Reconstruction to win a major statewide office.

The critical factor, Black said, was that Wilder showed a black candidate could amass substantial numbers of white votes in a southern state.

Several political veterans attributed the Wilder-Terry victories last night to a shift in the electorate in Virginia, the cradle of the old Confederacy.

"A Wilder victory shows the stereotype has been wrong all along," said Coleman. "These things don't just happen of the moment. It's an accumulation of demographics, of the changing face of the electorate. If the state were all 71-year-old white men, Wilder wouldn't win.

"Wilder's and Terry's victories are to Virginia what John Kennedy's victory was to the nation," he added. "It's particularly significant that Virginia, the leader of the Confederacy, is the first state in the South to elect a black."

The Democratic sweep also counts as a sizable asset to Robb's political fortunes, said the University of North Carolina's Black. "Robb is showing other Democrats in other places how you can still win in the South -- balancing the ticket and running candidates who are not really threatening," he said.

Robb, who leaves office in January and is expected by many to figure prominently in Democrats' plans nationally for 1988, campaigned hard for Wilder, a Richmond state senator, and for veteran state delegate Terry, the first woman to win statewide office in Virginia.

Terry, a 38-year-old lawyer who is single, was perceived less as a woman, said Roberts, than as "one of the boys. She paid her dues. She's not a militant."

"Wilder and Terry are considerably less frightening to whites and men, respectively, and were considered much more on their past records," said Austin Ranney, resident scholar at the American Enterprise Institute. "They are the kinds of blacks and women who are going to get elected, who don't represent a narrow constituency."

Jay Shropshire, state Senate clerk and a senior Democrat, called Wilder's effort "one of the best statewide campaigns I've ever seen. They started with three people in the basement of his law office in a state with a 15 percent black population and Wilder went out and sold himself to Virginia.

"I tip my hat to him," Shropshire said.

Several experts ascribed Wilder's victory to a campaign that soft-pedaled his past stands on civil rights, managed to appeal to white moderates as well as blacks and escaped unscathed from Republican attack.

"The Republicans certainly kept their gloves on," said Ranney, "partly because it might affect them adversely at the polls, but also because it would have offended them" to inject race into the campaign.

If Wilder had been running in North Carolina, said Black, "the Congressional Club -- the Helms bunch -- would have done a job on him all through the campaign."

Shropshire, the Senate clerk, praised Wilder's strategy of ignoring campaign statements by former governor Mills E. Godwin, a Republican and onetime segregationist. "He played it perfectly with Godwin," Shropshire said. "Godwin played right into his hands."

Eddie N. Williams, president of the black-oriented Joint Center for Political Studies, ticked off a laundry list of factors that he saw as boosting Wilder's fortunes.

"It Wilder's campaign was fairly low-key; he avoided overidentification with black voters; he controlled some of his instincts; he appeared as the tactful statesman; he made no major gaffes; he didn't pursue themes that Virginians may remember him for -- polarizing themes like civil rights -- and he demonstrated he was a team player," Williams said. "It helps to have the blessing of Robb and the ineptness of the opposition," he added.

Wilder, remembered in the state Senate for oratory attacking the Virginia state song as racially insensitive and supporting commemoration of Martin Luther King Jr.'s birthday, scored during the campaign with a television ad featuring a hefty-looking white deputy sheriff.

"To have a classic Southern law officer -- it was very impressive, dispelling the image that Wilder was something to be afraid of," said Roberts. "The ad said to people, 'If this guy can be happy with Wilder, maybe I can, too.' "

Wilder's strategy -- attempting to draw white voter support as well as black -- marked a distinct departure from last year's Rainbow Coalition campaign of the Rev. Jesse Jackson, which several experts said was perceived as "more black" in its message.

"I think Wilder symbolizes or personifies a new thrust in black political behavior among candidates who depend on majority white audiences to win," said the Joint Center's Williams