Virginia Democratic candidate for governor Gerald L. Baliles has maintained a strong 19 percentage-point lead over his opponent, Republican Wyatt B. Durrette, while Baliles' running mates have even greater leads going into the last days before Tuesday's elections, according to a new Washington Post poll.

The survey of 1,570 registered voters showed the Democratic ticket, which for the first time includes a black and a woman, performing strongly in all sections of the state and across all social and economic lines.

Baliles, 45, the former attorney general under Democratic Gov. Charles S. Robb, has amassed a 56 percent to 37 percent lead with 7 percent undecided in the poll, which was conducted over the three days that ended Thursday.

Baliles and Durrette were each up 6 percentage points from a previous Post poll. The initial poll, conducted Sept. 26 to Oct. 6, showed Baliles leading 50 percent to 31 percent with 19 percent undecided.

State Sen. L. Douglas Wilder, 54, a Richmond lawyer who is bidding to become the first black since Reconstruction elected to a major state office in the South, remained far ahead in the race for lieutenant governor.

The poll shows him leading Republican state Sen. John H. Chi- chester, 47, of Stafford County, by 24 percentage points, 58 to 34 percent with 8 percent undecided. That represents a 2 percentage-point increase over the lead Wilder had in the earlier Post poll.

The most dramatic movement in the poll came in the race for state attorney general. Democratic state Del. Mary Sue Terry, 38, of rural Patrick County, seeking to become the first woman elected statewide in Virginia, is leading by 32 percentage points, 61 to 29 percent with 10 percent undecided, in her race against Virginia Beach Del. W.R. (Buster) O'Brien, 39. The initial poll showed Terry ahead 43 to 27 percent with 30 percent undecided.

The new results show much larger leads for the Democrats than other published polls, including one in today's editions of the Richmond Times-Dispatch. That newspaper's poll, completed Tuesday, showed Baliles with a 5 percentage-point lead over Durrette, 45 to 40 percent. Wilder led Chichester by 9 percentage points (45 to 36 percent), and Terry was ahead of O'Brien by 19 percentage points (50 to 31 percent) in that poll.

The Times-Dispatch poll, using different methodology than the Post, is a random sample of 993 registered voters. The Post poll, also a random sample, takes into account people's statements about past voting, interest and intentions in the current election to determine a probable electorate.

Using the Times-Dispatch method, the Post results would show Baliles with a 15 percentage-point lead, Wilder ahead by 20 percentage points and Terry leading by 28 percentage points.

Democrats, campaigning with Robb in Southwest Virginia yesterday, said the Post poll supports what their polls have been showing.

"It underscores the sense of momentum we have detected in the last three or four weeks," said Baliles. "But we are not taking anything for granted. I'll be campaigning flat out until election day."

Robb described Tuesday as "a rendezvous with destiny," and Baliles said the election would represent "Virginia's renaissance on the national scene. Virginia will lead the nation again."

The three Republican candidates for statewide office, told of the poll's results during a campaign stop last night in Kingsport, Tenn., repudiated the findings.

"It's absurd," Durrette said, "It says more about the bias of The Post than about the status of the Virginia election, and that will be obvious on Tuesday. A lot of people in Northern Virginia who are fed up with the one-sided coverage of these races are going to wake up on Tuesday and say, 'We don't have to take it anymore.' "

Chichester said, "The people of Virginia probably have had a bellyful of the news media's bias, especially The Post's, and they will rebel against attempts by the media to dictate the outcome of this election."

The third man on the ticket, O'Brien, said, "I didn't put a whole lot of credence in it the last time. We just had our advertising started at the time the latest poll was taken . We're still encouraged."

Edward S. DeBolt, Durrette's Arlington-based consultant, also discounted the poll. "You guys are going to be embarrassed," he said. "I don't want to be quoted in this story. I don't want to dignify the poll. It's wrong . . . . We won't lose by 19 points."

Durrette announced in Roanoke yesterday that he would make an election eve trip to the White House tomorrow to meet briefly with President Reagan. "His support in what I expect to be a close election Tuesday is yet another major boost for my campaign and an important signal for the people of Virginia," the GOP nominee said.

"Well, that's one way to spend Monday," said Robb, when told of the visit. The governor said Durrette "must think it could help and is probably necessary . . . . It's modest help anytime the president of the United States indicates interest in a campaign, but you could argue how strong that interest is, however, is by how far he is willing to go to express it."

Reagan campaigned Oct. 9 for Durrette at an Arlington fund-raiser that netted about $500,000 for the campaign and has been featured in Durrette's TV commercials.

The Post survey showed Baliles maintaining or increasing his strength in nearly all sections of the state, including Northern Virginia where Baliles held a lead of 56 to 38 percent over Durrette. Durrette, who served as a legislator from northern Fairfax County from 1972 to 1977, has said he would easily win the region.

The Richmond area, where Durrette now lives, was the only area of the state in which he showed sharp gains, but he still trailed Baliles there, according to the poll.

Baliles, a former legislator from Richmond who defeated Durrette for attorney general in 1981, leads there by 7 percentage points in the new poll, 51 to 44 percent. The initial Post poll had shown Baliles leading there by 22 points, 54 to 32 percent with 14 percent undecided.

The Post's new survey, consisting of interviews with the people polled a month earlier, suggests strongly that about one-third of the voters have changed candidate preference in the governor's race one way or the other since Oct. 6.

About one of nine people who supported Baliles when first interviewed say they have now moved to Durrette, and about one in six who had earlier backed Durrette now put themselves in the Baliles column. Those who were undecided in that first poll appear to be breaking in the same pattern as the rest of the electorate: half for Baliles, a third for Durrette, and another third still uncertain.

In the lieutenant governor's race, one in 10 of Wilder's earlier supporters has shifted to Chichester, according to the new survey, but almost two in 10 of Chichester's previous backers now say they are for Wilder. In that race also, voters who were undecided tend to be dividing for the Democrat, in about a 4-to-3 ratio.

In the attorney general contest, by contrast, Terry lost only about one in 20 of her supporters to O'Brien and picked up about one in four of those who had been backing the Republican. In that race, the undecideds appear to be splitting about 5 to 3 for Terry.

In addition, Terry appeared to be drawing strong support from both men and women, suggesting early criticism that men generally would not be inclined to vote for a woman was inaccurate.

The poll also suggests that more Republicans this election intend to vote for the Democrats, a reversal of regular crossover patterns from most recent campaigns. The poll showed the candidates firming up their support among voters as the election nears, compared to the earlier Post survey that found that support for the two gubernatorial candidates was soft.

With Wilder on the Democratic ticket, the poll sample indicates that the election will see a sharp increase in black voter strength, as high as 20 percent of the turnout. Four years ago, blacks accounted for about 14 percent of the turnout. The higher percentage of blacks also could be attributed to a decline in interest among white voters, according to the poll.

Even if sizable black participation is discounted, the poll strongly suggests that Robb, the first Democratic governor in the state in 12 years, has succeeded in bringing many whites back into the Democratic Party. All three Democratic candidates are leading among white voters, a dramatic change from elections during the past 20 years.

All three Democrats have run moderate-to-conservative campaigns in which they have played down appeals to traditional Democratic constituencies, such as labor, civil rights leaders and teachers, in what they said was an effort to attract independents and moderates.

Forty percent of those interviewed by the Post were Republicans or lean Republican; 43 percent were Democratic or lean Democrat, and the remaining 17 percent were independents who do not lean one way or the other. When likelihood of voting is factored in, the Democratic portion increases slightly -- to 46 percent -- while the Republican ratio stays the same and independents decline to 14 percent.

Should the Post numbers be high for the Democrats, as critics charge, the contest in Virginia nevertheless is dramatically different from what it was at the outset when many political experts discounted or ridiculed the possibility of a black winning the state's second highest office.

Now Wilder seems a possible winner at a time when Virginia and the rest of the South are widely thought to be moving strongly toward the Republicans, in part as a backlash to the increased role of blacks in Democratic politics.

A victory by Wilder, no matter how narrow, in one of the region's most conservative states likely would force a rethinking of partisan realignment.

It could "send a message to blacks in the South that you don't have to run exclusively as a black candidate," said Jeremy Plant, associate professor of government at George Mason University. He said a win could show "that a black can win if he does a good job campaigning and building support with traditional groups . . . that race can be factored out."

In addition to the statewide races, voters Tuesday will cast ballots for the 100-member House of Delegates, including several closely contested races in Northern Virginia.

In Arlington, voters will will elect a member of the County Board, and Alexandria voters will decide a race for sheriff.