The letters started flowing from a converted warehouse in Richmond several months ago -- urgent appeals for money to save Virginia from the horrors of Sen. Edward M. Kennedy and labor union bosses.

In one letter, Virginia Democrat Richard J. Davis is portrayed as a defender of labor union officials who "commit violence and extortion." In others, Kennedy and the national Democratic party are reported ready to spend "record amounts" to rob Virginia of a conservative voice in the U.S. Senate.

These and other missives on behalf of Republican Senate candidate Paul S. Trible Jr. are examples of the kind of sophisticated GOP direct mail operations that have changed the nature of political campaigns in Virginia and many other states in recent years. Using three separate consultants, armed with dozens of mailing lists that have been swapped, bartered and rented in the marketplace of conservative and Republican fundraisers, Trible's campaign expects to pull in more than $350,000 through direct mail this year -- more than three and one half times his costs.

Virginia Republicans, in fact, proudly proclaim themselves to be in the vanguard of direct mail politics -- a modern-day mix of computer technology and raw emotionalism. When a Trible mailing goes out, its recipients are selected from a computer data base that includes the names and financial contributing history of about 50,000 past donors to Republican campaigns in the state.

"Virginia has been at the leading edge," says William Royall, president of the Richmond-based North American Marketing Corp., a state-of-the-art direct mail company that works for Trible's campaign as well as most of the state's Republican congressional candidates. "There are very few political parties that have the sophistication we have."

In fact, the Virginia GOP has one computerized list that has been used by Trible that includes the names and addresses of all 2.1 million registered voters in the state and their political preferences. These direct mail operations also have brought the Republicans a storm of criticism this year, throwing the public spotlight on one of the murkier and least understood aspects of modern campaigns. Democrats, whose direct mail pitches are primitive by comparsion, charge that Trible's carefully targeted and emotional appeals have been tantamount to a silent and subterranean smear campaign.

"It's like it's almost acceptable if you lie through the mails, but not if you do it on television and radio," says James Carville, Davis campaign manager. "It's a deliberate attempt to inflame people."

Others experts say, however, that the "lies" and "distortions" that Davis campaign complains about are simply standard fare in most modern direct mail operations.

Indeed, while Davis' own direct mail letters have been relatively tame (and will only raise about $100,000, according to his aides) his campaign benefits indirectly from scores of fiery national Democratic party mailings that paint Republican candidates this year as tools of "fanatical organizations" associated with the "Extreme Political Right and the Religious New Right."

"You have to get a person mad, happy, excited or miserable in order to stimulate a contribution," says Larry Sabato, a University of Virginia professor and author of "The Rise of Political Consultants." "So exaggeration and distortion go hand in hand in most direct mail . . . But it's proven effective. Direct mail is a silent killer."

For their part, Trible's strategists defend their mailings as legitimite efforts to highlight differences between the candidates. "I'd be very happy to put them on the front page of The Washington Post," says Robert Weed, a top Trible campaign strategist.

But while the basic message may be "the issues," the direct mail letters employ far more vivid imagery than Trible himself has used on the stump. Consider Trible's direct mail attack on Davis' opposition to a proposed change in the Hobbs Act, a 1946 anti-racketeering law. Davis -- along with the Reagan administration -- has opposed an amendment to the act that would make picket line violence by union members a federal crime, arguing that such violence can be prosecuted more effectively at the state level.

"So crossing state lines to commit violence and extortion is okay if you are a union official," writes Trible in one of his direct mail letters. "Only the most ideological liberal would defend this special privilege. Dick Davis defends it. Can you trust this man to represent the conservative views of the majority of Virginians?"

The specter of Kennedy as arch-symbol of Democratic liberalism is conjured up again and again. "Ted Kennedy wants Dick Davis to win," writes former Virginia Gov. John N. Dalton in one letter for Trible. "Ted Kennedy does not like being part of the minority party in the Senate. A Davis victory could change this."

One of the more recent innovations in direct mail fundraising has been the "wife letter," a folksy appeal for money from the candidate's spouse. Several thousand Trible supporters in his Newport News congressional district recently received such a handwritten letter from Trible's wife, Rosemary. It was mass-produced on what appears to be her personal stationary and is complete with chatty details:

"The momentum of the campaign is increasing daily to the point that Paul and I see each other only on weekends . . . I would love to have $35,000 to give Paul on September 24," the letter says.

Another direct mail gimmick is to mail out purportedly private campaign budgets which either inflate or understate the candidate's financial situation depending on the need. Early in the campaign, Trible sent out elaborate glossy campaign kits which included an admittedly exaggerated campaign budget of nearly $2.8 million. Its aim was to convince skeptics, particularly among the Washington-based political action committees, that Trible had a well-financed campaign and was a likely winner.

More recently, however, the direct mail letters have begun to appeal for "emergency" contributions while appearing to exaggerate Davis' own finances. "Dick Davis is spending approximately one million dollars in October for media . . . Paul cannot hope to match this tremendous outlay of cash in such a short time," writes Dalton in a letter that went out last week.

This assessment of Davis' media budget would appear to clash with Davis' latest Federal Election Comission financial report, which shows he had raised only $622,000 for the entire campaign through Sept. 30.

The linchpin of Trible's direct mail campaign is Royall, a 36-year-old Republican party strategist whose IBM computers in a Richmond industrial park contain the master file of Virginia Republican donors, lists refined from a decade of mailings. For a typical mailing of 50,000 letters, Trible's campaign will pay Royall $13,500 and raise about $60,000.

Early in the campaign, Royall "prospected" for Trible -- renting lists from independent brokers that sold under such titles as "Best Conservative Working Names" and "Pro-American Master File." The purpose was to identify potential new contributors rather than to spread the candidate's message. Now his appeals are fired at more precise targets.

"If I want to do a letter from George Bush, I'll just say, give me the names of everybody who gave to Ronald Reagan and Wyatt Durrette the GOP's candidate for state attorney general -- figuring that will give me people who are hard-core Republicans," says Royall. "Then I might test mail it in the Richmond area to see the response, or switch off to do Reagan, Durrette and Sen. John W. Warner contributors. The Democrats can't do anything like that."

Trible also has begun a last-minute "persuasion" direct-mail effort coordinated by Ed Debolt of Arlington, the president of DCM Inc., a longtime Republican consultant and former associate of Royall. The key to persuasion direct mail is using polling data to coordinate specific issue-oriented appeals to particular groups. It was a lesson DeBolt and Royall first learned during the 1977 gubernatorial race between Dalton and Henry E. Howell.

"In August, Dalton was way behind in the polls, but we noticed that half the undecideds were in Northern Virginia," recalls Royall. "And most of them were homeowners, with incomes over $30,000. So we overlaid the census tracts and wrote a letter for that group.

"We sent out 400,000 letters in one week and we saw Dalton go up six points in the polls," said Royall. "I said, 'This is the closest thing to magic I've ever seen.' "