U.S. Senate candidate Richard J. Davis thought he had hit upon a near-perfect issue to score with Virginia voters -- Republican Paul S. Trible's attendance record.

For the last week, the Democratic lieutenant governor, who is running slightly behind in the polls, has spent $50,000 for a hard-hitting radio commercial charging that Trible's record for absenteeism ranks him "399th out of 435 members of the House in attendance."

"There are few of us with jobs that could keep our jobs with that kind of attendance record -- let alone ask for a promotion," states an announcer in the Davis commercial.

But now Trible believes he has found the ideal counterattack: Davis' attendance record. According to figures released by the Trible campaign, Davis missed 37 of 137 City Council meetings during his last four years as mayor of Portsmouth, giving the Democratic candidate a lower attendance percentage at the Council than Trible had in the House.

"Paul Trible's record is less than 90 percent, but Dick Davis' was less than 80 percent," said Bob Weed, Trible's chief campaign strategist. "It tells you a lot about a guy that he would make an issue about something when his own record is worse."

The latest flap in the Senate campaign comes on the heels of recent scrapes over campaign memos and fund-raising tactics in which the two candidates have accused each other of going to great lengths to avoid talking about "the issues," such as the economy or national defense.

And like the earlier disputes -- in which Davis has blasted Trible with "malicious falsehoods" and Trible has charged Davis with "name-calling" -- the absenteeism battle quickly took a nasty turn. A Davis campaign spokesman angrily charged Friday that Trible's campaign was exploiting the illness of Davis' wife, Martha, who is suffering from cancer.

Many of Davis' absenses in Portsmouth were because of Mrs. Davis' illness, said Will Marshall, Davis' press secretary. "They know full well about his wife, they know what the story is," said Marshall.

Besides, said Marshall, Davis' absences at a part-time mayor's job paying $4,000 a year cannot be compared with Trible's record "as a big-time congressman who's paid $60,000 a year."

Absenteeism, however, is certainly not a novel issue for members of Congress running for higher office. Sen. Edward M. Kennedy, for example, made only 18 percent of the votes in the Senate in 1980 when he was running for president, according to figures compiled by Congressional Quarterly. Nevertheless, the issue could loom large in this year's campaign to fill the seat of retiring Sen. Harry F. Byrd, Jr., who often boasted about his diligence in showing up for roll-call votes.

It is also an issue that, the Davis campaign believes, is exploited with effectiveness in their radio commercial, devised by media consultant Robert Squier and campaign manager James Carville. "A lot of people are talking about it," says Marshall.

The 30-second commercial is part of a $270,000 Davis media offensive that includes a series of new television spots that began showing this weekend on such prime-time shows as "Dallas." The radio ad, however, is the only negative spot. In it, an announcer plays off Trible's claimed expertise on military affairs by clicking off the votes he missed in the House: "On the vote to strip the Nimitz class aircraft carrier, the cruise missile -- absent. The Pershing II missile, the MX missile, the C5 cargo aircraft -- Trible absent. Or, as they say in the service, Trible: absent without leave."

Trible strategist Weed said the Davis commercial was deceptive because most of the big-ticket military items cited were, in fact, on one amendment last spring offered by Rep. Ronald Dellums (D-Calif.) "to wipe out the entire defense budget." The amendment failed, 345-to-55, "so that was not one where Trible's persuasiveness or extra votes were particularly needed."