Former Virginia Lt. Gov. Henry E. Howell moved into a strong lead last night over former Attorney General Andrew P. Miller in the race for the Democratic nomination for governor of Virginia.

With more than three-fourths of the vote counted, Howell, 56, who forged ahead during the evening, held a 52 to 48 per cent lead over Miller, 44.

Charles S. (Chuck) Robb, of McLean, the 37-year-old son-in-law of former President Lyndon B. Johnson, took a strong lead for the nomination for lieutenant governor over state legistors Richard S. (Major) Reynolds of Richmond, heir to the Reynolds metal fortune, and Ira M. Lechner of Arlington, Robb, running for his first public office, spent more than $336,000 and campaigned with his wife, Lynda Bird and his mother-in-law, Lady Bird Johnson, to win the largely ceremonial, $10,500-a-year job.

Del. Edward E. Lance of Richmond, the conservative chairman of the Virginia House Appropriations Committee, easily defeated three opponents to win the Democratic nomination for attorney general. Lane, 53, outdistanced Del. Erwin S. (Shad) Solomon of Bath County, John T. Schell of Fairfax County and Del. John L. Melnick of Arlington.

The light turnout was generally believed to be a boon to Howell, whose campaign was plagued by persistent financial and organizational problems. A Miller spokesman said last night that the light rain that fell over much of the state yesterday had hampered their organization's ability to produce a heavy Miller vote.

Miller's vote fell short of his staff's expectations in Northern Virginia, the only region of the state where Miller failed to place television advertising and and one of the few areas where Howell did. In early returns, Howell was carrying populous Fairfax County by a slim margin and won Arlington by a 4-to-3 margin.

There, as elsewhere, Howell appeared to be benefiting from a campaign that stressed his longrecord of fighting against the "big boys" of Virginia's political and economic establishment and his friendship with President Carter. Miller, the son of a man who 28 years ago made the first serious challenge to the Bryd Organization, ran as an experienced administrator won would have the best chance of being elected in a race against the Republican's nominee, Lt. Gov. John N. Dalton, in November.

A Washington Post poll of Virginia voters at 21 precincts selected at random throughout the state gave a picture of a primary election in which the champion of the Virginia Democratic Party's left wing, Howell, was pitted against the champion of the right wing, Miller.

On the basis of early poll returns, Howell was getting the votes of three out of every four persons who identified themselves as liberals. Miller was getting six out of 10 votes among those who identified themselves as conservatives.

In the struggle for the middle ground, Miller was getting a majority of those voters who identified themselves as moderates.

The results of the poll conducted by the Post's editor for political surveys, Barry Sussman, made it clear that race and racial issues played a major role in the election results. Howell got nine out of every 10 black votes in early statewide returns. In the heavily black urban areas of the lower James River basin - from Richmond and Petersburg in the west to Norfolk in the east - Howell's majority among blacks exceeded 90 per cent.

Miller was making modest inroads into the black electorate in the small cities and rural areas of Central Virginia, but even in that region Howell was getting more than eight out of 10 black votes.

During the campaign Howell collected most of the endorsements from major black political organizations but Miller's organization kept up a small, well-focused drive to take away as much of Howell's traditional black support as possible.

Miller's black-voter coordinator, Larry Jones, traveled the state with the arguement that Howell had exhausted his political capital in two unsuccessful races for governor and that Miller was a winner who offered the best chance for blacks to gain a stake in the next administration.

Because of this effort and Miller's successes with black voters in his two races for attorney general, even Howell supporters thought Miller might win a significant slice of the black vote.

In an unguarded moment early in the campaign, Howell himself conceded 25 per cent to Miller. Miller insisted just before the election that he would do better than that.

Miller was collecting a substantial majority of the white vote in early returns and among the whote voters there appeared to be a clear correlation between attitudes on racial issues and the voters' candidate.

Out of voters questioned in The Post poll who said integration of the races is going too fast or at about the right pace, six out of 10 voted for Miller. Howell, on the other hand, got seven out of 10 votes in early returns from persons who said racial integration is not going fast enough.

The poll showed a striking correlation between the gubernational primary and last year's presidential election results in Virginia, with Howell drawing his strength from those who voted for President Carter and Miller from those who voted for former President Ford.

Six out of 10 said they voted for Carter also said they voted yesterday for Howell. Seven out of 10 who said they voted for Ford also said they voted for Miller.

The poll results thus confirm the view that most experienced political figures in the state held of this primary.In that view, success for Miller would depend on his ability to turn out a large vote by the moderate-conservative majority in the Virginia electorate that has been drifting from Democratic to independent or even Republican identification during the last decade.

The poll also showed that only a small majority of those who voted yesterday in the statewide Democratic primary were Democrats. Only six out of 10 voters surveyed identified themselves as Democrats. One-third said they were independents and one out of 16 admitted they were Republicans.

Virginia election laws do not provide for registration by partly and voting in a party primary is open to all registered voters.

Howell's nearly 30 years in public life as a colorful advocate of civil rights, consumer protection, tax reform and equality in legislative apportionment clearly were assets in his race against Miller.

The poll showed, on the basis of early returns, that a majority of all voters thought Howell would do better than Miller in dealing with tax and public utility issues.

Black voters rated Howell as more able to provide honest government and deal with racial issues. White voters were evenly divided between Howell and Miller on those questions.

The primary contest was one of the longest election campaigns in the state's history. Howell announced his candidacy in late 1975 and Miller shortly after that.