Democratic senatorial candidate Richard J. Davis, in a demonstration of political bitterness rarely seen in Virginia politics, denounced yesterday a memo written by the campaign manager of his Republican opponent as a collection of "malicious falsehoods" and demanded an apology.

Supporters of Republican candidate Paul S. Trible Jr. defended the accuracy of the memo, refused to apologize and responded with a salvo of their own. "I really think they're reaching for straws," said Betsy Weinschel, one of Trible's media consultants. "We're very much ahead, and I'm sure they're scared. Their fund-raising isn't going very well."

Yesterday's dispute began when the Davis campaign released a copy of the Aug. 11 appeal "to friends of Paul Trible" from his campaign chairman, Judy Peachee. The Trible memo alleged that Davis campaign workers had shown eight Davis television advertisements to representatives of 75 labor unions at a recent meeting in New York.

Quoting an anonymous "reliable source," the memo charged that the Davis workers then asked the labor representatives to contribute $3,000 each to the Davis campaign, but to withhold those contributions until after the Sept. 30 reporting deadline set by the Federal Elections Commission.

"If this report is factual in all aspects," the memo continued, "it would mean that the labor unions would be contributing $225,000 for an October media blitz."

James Carville, Davis' campaign manager, characterized the memo as "so ludicrous that it's difficult to comprehend." He said that no member of Davis' staff had attended the meeting, nor had any solicitations been made. "We don't even have any TV spots," Carville said.

Trible's press secretary, Neil Cotiaux, defended the memo, which he described as an internal GOP document, but refused to reveal the source of the information. "I have been absolutely swamped with phone calls today, and the last thing I've had time to do is to trace back to the source of the material," he said. Trible and Peachee, campaigning in southwest Virginia, could not be reached for comment.

The intensity of yesterday's political firestorm was extraodinary by Virginia's gentlemanly political standards, and seemed reminiscent of the mud-slinging media campaign state voters saw during last year's gubernatorial campaign.

That campaign between Gov. Charles S. Robb and his Republican opponent, J. Marshall Coleman, was among the nastiest in Virginia history.

Davis aides painted the Trible memo as an indication that the Trible campaign is consumed by desperation following a recent publicized but unreleased Davis poll that supposedly showed Davis leading by 5 percentage points. "Mr. Trible is just getting desperate and has decided that if he can't beat Mr. Davis he'll run against labor," said John Perkins, director of the Committee on Political Education (COPE), the political fund-raising arm of the AFL-CIO that sponsored the New York labor meeting.

Trible supporters say the desperation lies with Lt. Gov. Davis, a 60-year-old mortgage banker who lags far behind his Republican opponent in raising funds, and who recently saw W. Roy Smith, the leader of the state's wealthy and influential conservative coalition, throw his support to Trible. As of last month, Davis' campaign had raised only $32,465 to Trible's $520,983.

"There is a direct correlation between the Davis statement today and the massive coalition support that Congressman Trible has received this week," Cotiaux said. "I think they're attempting to stop us in our tracks among members of the coalition, and I don't think it will succeed."