For 10 years, the polarizing populism of Henry E. Howell Jr. and the conservative bugle calls of Mills E. Godwin Jr. and Harry F. Byrd Jr. dominated Virginia politics and submerged the role of the state's political parties.

But 1978 is the year of the party in the Old Dominion - a do-or-die time for Democrats long splintered by factionalism and a season of challenge for a resurgent state GOP taking the field with a politicially untested candidate.

In addition to the race for the seat of retiring Republican Sen. William L. Scott, a number of congressional contests and a nonpartisan campaign to legalize horse-race betting are on the Nov. 7 ballot in Virginia.

Neither Democrat Andrew P. Miller nor Republican John W. Warner inspire the intense loyalties or opposition generated by a Howell, Godwin or Byrd, and their candidacies for the U.S. Senate have thus become a measure of party, as well as personal, appeal.

The focus of party energy on the Senate race is all the greater because of the lack of competition for most of the state's other 10 congressional seats. Five of the House incumbents are unopposed or face only token opposition. Only in Northern Virginia's 8th District is the incumbent thought to be seriously threatened.

In the 8th District, two-term liberal Democrat Herbert E. Harris II is being challenged by conservative Republican John F. (Jack) Herrity, chairman of the Fairfax County Board of Supervisors.

Both Senate candidates have acknowledged the importance of their race to party fortunes. As he campaigned for the nomination in a field of eight last spring, Miller warned, "If we fail to do it this year the long dry spell could turn into a drought."

Virginia is the only state in the nation that has failed to elect a Democratic candidate to the governorship or U.S. Senate in the last 10 years. Should they fail this year, Democrats will not have another chance until the 1981 gubernatorial election.

Campaigning for the nomination on his ability to win elections - he served two terms as attorney general, Miller predicted that a Senate defeat this year would make it difficult for Lt. Gov. Charles S. (Chuck) Robb to capture the governor's mansion for the party in 1981.

RObb is considered the leading candidate for the Democratic nomination and has been campaigning heavily for Miller.

Warner, in a recent interview, said Democratic conservatives who have defected from the coalition that helped produce past Republican victories did so out of concern over the impact of the Senate race on Robb's fortunes.

"These are Democrats who think they have a good candidate for governor in 1981," he said, "and they are afraid he won't make it unless they get some momentum going this year."

Warner was nominated by the Republican State Central Committee on Aug. 12 to succeed the late Richard D. Obenshain, who was killed in an Aug. 2 plane crash.

The Senate candidates are avoiding involvement in the campaigns for and against horse-race betting, an issue expected to generate as much controversy among voters as it has for a decade in the General Assembly.

The legislators finally voted to put the question to a referendum in its session earlier this year. If it is approved, residents of the city or county in which a track site is proposed will have another chance to vote on parimutuel betting in their locality.

In addition to the Harris-Herrity contest in the 8th District, major candidates are opposing each other in four other congressional districts.

In Northern Virginia's 10th District, incumbent Democrat Joseph L. Fisher is opposed by Republican Frank L. Wolf. In the 7th District which sprawls from the Fredericksburg area west to the lower Shenandoah Valley, incumbent Republican J. Kenneth Robinson is opposed by Democratic State Del. Lewis P. Fickett Jr.

In eastern Virginia's 1st District, first term Republican Paul S. Trible is opposed by Democrat Lewis B. Puller and in southwest Virginia's 9th District, incumbent Republican William C. Wampler is opposed by Democrat C. Champ Clark.

All of the incumbent were favored to win these races, making it likely that Republicans will continue to hold at least a 6 to 4 edge in the congressional delegation, depending on the outcome of the Harris-Herrity race.

In addition to the referendum on track betting, voters also will be asked to approve or reject a constitutional amendment permitting tax exemptions for property that has been renovated or rehabilitated. The proposal is intended to stimulate private urban renewal.