Del. Edward E. Lane, a conservative Democrat from Richmond who supported Richard M. Nixon in 1972 and considered running for governor as an independent earlier this year, has announced his candidacy for the Democratic nomination for attorney general.

Speaking at a press conference in Richmond's venerable John Marshall Hotel, the scene of many political announcements, Lane said he had decided a bid for governor as an independent was "impractical" because the "chance of success was not reasonable."

Lane, a member of the House of Delegates since 1954, faces Del. John L. Melnick (D-Arlington) and lawyer John Schell in the June Democratic primary.

The Republicans will be choosing their nominees for the three statewide offices coming up this year at a convention in June. So far, Del, Wyatt B. Durrette Jr. (R-Fairfax) and Sen. J. Marshall Coleman (R-Staunton) have announced they are contenders for the party's attorney general nomination.

Lane's announcement is considered by many legislators to hamper Melnick's chances because of the senior delegate's long years of service and popularity in the populous Richmond area. Schell, a lawyer who has represented consumer groups but has not previously been elected to public office, is not very well known.

But Melnick sees it differently. "His record shows he's always ready to jump out of the party," melnick said. "I've been a Democrat through good and bad. Actually I think this will make a more interesting race."

Lane, a corporate lawyer, said he expects to spend about $400,000 on the primary race and the general election, should he win the primary. Melnick said this is more than he expects to spend.

Should he win, Lane would have to leave his position as head of the influential Appropriations Committee in the House, leaving the vacancy to he filled by Alexandria Democrat James M. Thomson, the House majority leader.

In response to questions, Lane said he would not announce a preference for either of the gubernational candidates - Andrew P. Miller or Henry Howell. Nor would he hint at his preference, and maintained vehemently that he was running independently and would not be a part of the ticket before the primary.

He describes himself as a "fiscal conservative" and on other matters as a "progressive." However, his candicacy is viewed by many, including Melnick, as a resurgence of the conservative old guard of the Democratic party.

Lane was among those who was publicly disenchanted when the "liberals" supposedly took over the party leadership in 1972. Henry Howell has often defined a liberal in Virginia as "someone who believes in life after birth."

In 1972 Lane said, according to a newspaper clipping provided by Melnick, that he was available to run for governor either as an independent or a Republican. His brief flirtation with an independent gubenatorial bid this year was dumped after a private poll showed his chances were not very favorable.

"I think everyone in the General Assembly would like to be governor," he said at the press conference in response to questions about his future aspirations.