Richard J. Davis, Virginia's Democratic candidate for lieutenant governor, demanded yesterday that state Attorney General J. Marshall Coleman investigate charges that his Republican running mate violated the state's conflict of interest law by promoting legislation that benefitted his legal clients.

Davis, in his sharpest attack yet on state Sen. Nathan H. Miller, sought to tie allegations surrounding his GOP opponent with similar charges that yesterday forced the resignation of Northern Virginia highway commissioner William B. Wrench.

"If the attorney general is so sensitive to conflict of interest cases, why has he failed to investigate the classic example his running mate offers him?" Davis asked during a campaign speech in Leesburg. "Could it be that the attorney general is allowing political fortunes to dictate the legal system in Virginia?"

A spokesman for Coleman said yesterday the attorney general had no plans to investigate Miller. "There is no conflict," said Coleman spokesman David Blee. "I think Nathan has aired the matter fully."

Miller later replied that any question about his conduct was a matter for the state Senate to decide and angrily accused Davis of attempting to raise a bogus issue. "We seem to have arrived at a campaign crossroads and I am disappointed that my opponent has now taken the low road," Miller said. "He is becoming proficient in two categories: first, how to run a campaign without ever talking about the issues and second, how to cast red herrings about in an attempt to hide the fact that he will not talk about the issues."

Coleman this week investigated Wrench after it became known the highway commissioner had been instrumental in routing the proposed Springfield Bypass near some of his Fairfax County properties. In a report released Thursday, Coleman concluded that Wrench violated the spirit of the state's conflict of interest law.

Miller, 38, a Harrisonburg lawyer, has conceded that there is "an apparent conflict of interest" in his dual roles as an attorney drafting bills for his clients, the state's electric cooperatives, and as a state legislator voting for those bills. He insists he has violated no law and that other lawyer-legislators often vote for bills that benefit their clients.

Miller's supporters were swift in denouncing Davis. "This is an absurd request on its face," said state Sen. Wiley F. Mitchell Jr. (R-Alexandria), a top Miller campaign adviser. "It reveals a notorious lack of understanding about the way the Senate operates."

Noting that the major job of the Virginia lieutenant governor is to preside over the 40-member Senate, Mitchell, a Washington lawyer, sought to ridicule Davis. "It seems particularly ironic that (Davis) is seeking to preside over the Senate," Mitchell said. "He doesn't know how it works."

Aides to Davis, who has previously attempted to downplay the controversy over Miller, countered that the Republican was attempting to evade the issue by raising procedural questions.

"This is a clear opportunity for the attorney general to see if Nathan Miller has violated the conflict of interest law and the lobbying law," said Bobby Watson, Davis' campaign manager. "Maybe Marshall Coleman doesn't understand the work of Virginia government because he's been too busy campaigning."

Conflict of interest charges have been dogging the Miller campaign since Aug. 5 when The Washington Post disclosed that Miller had accepted more than $250,000 in legal fees while privately drafting and then voting for legislation that gave his legal clients $13.2 million in tax breaks and business advantages.

"For a while it seemed that Dick was content to let other people beat on Miller for a while," said one Republican adviser. "Now he's doing it personally, which I presume to mean that everyone else has lost interest."

A statewide poll released this week by two television stations showed Miller lagging five points behind Davis, but Miller campaign officials said yesterday the conflict of interest issue has had no adverse effect on their candidate's popularity.