After a lumbering start that had some Virginia Democrats worried, Lt. Gov. Richard J. Davis' campaign for the U.S. Senate has finally begun to take shape with the recruitment of two nationally known political consultants who helped put together last year's triumph for Gov. Charles S. Robb.

With the aid of a key Robb adviser, Davis recently persuaded adman Robert Squier and pollster Peter Hart to sign on for Davis' fall race against Republican Rep. Paul S. Trible. The retention of the two veteran Democratic consultants--Squier filmed TV ads for Jimmy Carter's 1976 presidential campaign, among others, while Hart polled for Sen. Edward Kennedy's 1980 race--had Davis staffers boasting this week of a major campaign coup.

"These guys are, by anybody's definition, the finest in the country," said James Carville, a lanky Louisiana lawyer who last week was hired as Davis' campaign manager. "This isn't just major league; this is all-star."

As far as some Democrats view it, though, the influx of Washington talent couldn't have come a moment too soon. The Davis campaign began more than a month ago as a consultant's nightmare: After being drafted as the Senate nominee at the party's Roanoke convention, the 60-year-old Portsmouth mortgage banker found himself thrust into a race without a campaign organization or headquarters, much less a strategy. Not only was there no campaign money in the bank, Davis was still paying off a $50,000 debt from his race last year for lieutenant governor.

The organizational void forced Davis to shun public appearances and spend his first month as a candidate concentrating on what staffers call "nuts and bolts"--attending rounds of unpublicized, one-on-one visits with potential money-raisers, hiring a campaign staff, and finding a headquarters.

To some Democrats, those problems only underscored the gap with Trible, who has had a state organization in place since February. The GOP nominee already has sent out about 100,000 mailings, and is expected to top the $500,000 mark when new campaign finance reports are released next week.

"It's been dead in the water up here," said Fairfax Commonwealth's Attorney Robert F. Horan, of the Davis campaign. "There's not any momentum even beginning to generate . . . I don't even know who's running the show."

The fretting of the party rank and file, however, has been dismissed by Davis aides who say there is plenty of time before the Nov. 2 election and that Senate politics are about the last thing that concern most Virginians during the summer. And the candidate himself, serenely picking crabs at a Kings Dominion cancer benefit Thursday night, insisted he was in no hurry to rush headlong into combat with his Republican opponent.

"You know between Labor Day and November, the public will be so tired of hearing about Paul Trible and Dick Davis that they won't have any interest at all," said Davis.

"I'm very pleased with the progress that we've made," he added. "We've put together a good organization . . . Of course it would be irrational to expect that we'd be as organzied as Paul is--he's had four years to get ready."

Another focus of Davis' efforts has been to court the state's "coalitionists"--those influential conservative independents, closely identified with the retiring Sen. Harry F. Byrd Jr. A few days after his nomination, Davis paid a call on former Democratic legislator W. Roy Smith of Petersburg, who has spearheaded committees for both Republican and Democratic candidates. More recently, Davis also visited former Republican Gov. Mills E. Godwin of Suffolk, who has endorsed Trible.

"We've been trying to enlist the support of many of the people who would have supported Harry Byrd if he would have run," Davis said. Yet in most cases, Trible has been there first. And one Republican source says the party is "optimistic" that Trible soon will have his own coalitionist committee.

One area where Davis has had grounds for optimism is in the role being played by top Robb fund-raisers and advisers, such as lobbyist William G. Thomas of Alexandria, state Del. Alson Smith of Winchester, and Richmond stockbroker McLain O'Ferrall. Before the convention, the failure of moneymen such as Thomas and O'Ferrall to enthusiastically back his candidacy was a major reason for Davis' agonizing over accepting the nomination.

Thomas said this week that he, O'Ferrall and Smith have been putting together a 300-member finance committee that should be announced shortly. In addition, Thomas, considered Robb's closest political adviser, handled the recruiting of Squier, arranging a meeting two weeks ago in his Old Town law office between the adman and Davis.

It was out of that meeting that Squier says the likely central theme of the Davis campaign began to take form--the contrast between the older Democrat and his youthful challenger. "Trible is a fairly unseasoned young man," says Squier, whose instincts for the jugular were shown in a series of tough ads he devised for Robb last year. "He Trible just doesn't have the kind of resume and credentials of Davis--a war hero, a successful businessman. The first thing I go for in a candidate is character and that's a great advantage that Davis has."

Republicans say they are more than willing to meet Davis head-on on the issue. "If they want to talk about experience, fine," says Judy Peachee, Trible's campaign manager. "Paul's been in the Congress for six years; Davis has been lieutenant governor for six months. Paul's cast 6,000 votes. How many votes has Davis cast? What is experience--having grey hair or being on the front lines?"

Despite his moderate to liberal image, Davis has yet to take specific stands on many issues, other than to criticize Reagan administration economic policies while portraying himself as a "fiscal conservative." Pollster Hart says he "couldn't be more pleased" by the contrast between Davis' lack of specifics on issues and Trible's voting record.

"You have in Paul Trible a 110 percent Ronald Reagan supporter," says Hart. "He's got to answer for an awful lot of those votes, his leaning for the privileged and the special interests."

Moreover, Hart added that his own preliminary polling in one Virginia congressional district shows that Trible's headstart has added up for naught in terms of voter perceptions. "It was a dead-heat with a huge undecided," said Hart. "I think they're both at ground zero."