The top official of the Virginia Democratic Party is expected to resign Friday, triggering a contest for his job that could further divide state Democrats already stunned by the smashing Republican electoral victory earlier this week.

State Party Chairman Richard J. Davis said several months ago he planned to resign immediately after Tuesday's election and declare himself a candidate for lieutenant governor. But Davis reportedly will announce only his resignation tomorrow. He is expected to delay a decision to run for office for several weeks while he attempts to assess the impact of the GOP landslide on his 1981 prospects.

Davis is only one of several prospective Democratic candidates for statewide office said to be pulling back in the face of Tuesday's disaster. President Carter lost Virginia by 230,000 votes, dragging down with him the party's two Northern Virginia members of Congress, Reps. Herbert Harris and Joseph Fisher.

State Senate Majority Leader Hunter B. Andrews of Hampton, also considered a possible candidate for govenor or lieutenant governor, said a number of Democrats were being forced to reconsider their plans. Andrews did not comment on his own intentions.

Davis, who was unavailable for comment today, apparently plans to ignore pleas from several party leaders who wanted him to delay his move for at least a few weeks. They were concerned that his resignation, following so quickly on the heels of the election, would leave the impression that the party structure had been decimated by the defeat -- the latest in a decade-long record of setbacks.

The resignation, to take effect Nov. 22, has already set off competition between party conservatives and liberals over Davis' successor. The party's moderate-to-conservative wing, under the direction of Davis and Lt. Gov. Charles S. Robb, is said to back Virginia Beach Del. Owen Pickett.

Party liberals, who have lost control to the Robb faction in recent years, reportedly are supporting H. R. (Peck) Humphreys, a businessman from the Northern Neck area fronting the Chesapeake Bay. Humphreys has the backing of former lieutenant governor Henry Howell, the party's unsuccessful gubernatorial candidate in 1977.

Both men have begun telephoning potential supporters throughout the state in anticipation of a party central committee meeting Nov. 22. Party leaders may also decide when whether to pick their statewide candidates by primaries or a convention next year.

Davis, who has alredy set up a "Friends of Dick Davis" campaign committee with a Richmond headquarters and six full-time employes, is said to be an all-but-certain candidate despite Tuesday's debacle. Others mentioned as possible opponents include Andrews, former Arlington delegate Ira Lechner, who lost a bid for the party nomination in 1977, and state Sen. Dudley J. Emick of Fincastle in Southwest Virginia.

Robb, who is likely to win the party's gubernatorial nomination without opposition, said yesterday Tuesday's election results would not deter him from running. He has not revealed when he plans to announce his candidacy.