Virginia Attorney General J. Marshall Coleman comes to the Republican state convention this weekend assured of his party's gubenatorial nomination but still perceived as trailing Democratic opponent Charles S. Robb and beset by criticism from both the moderate and conservative wings of his party.

Many party officials believe the Coleman campaign's hyperactive swirl of public appearances, position papers and a $250,000 television and radio ad campaign has succeeded in narrowing the voter recognition gap between him and Robb, famous because he is Lyndon Johnson's son-in-law. But it has also alienated many in the GOP establishment.

Party moderates identified with former governor Linwood Holton have criticized Coleman for supporting Gov. John N. Dalton's veto of a bill that would have made slain civil rights leader Martin Luther King's birthday a state holiday. Holton himself won't comment but has told friends he thought Coleman's support, part of an effort to placate party conservatives, a critical mistake.

Although pleased with the veto, conservatives close to former governor Mills Godwin have denounced Coleman's pledge of no state tax increases during his term if elected. "That kind of inflexible approach is just plain irresponsible," says former state Appropriations Chairman W. Roy Smith, a Richmond pharmaceuticals executive and close Godwin ally, who adds, "I haven't heard a single person conment favorably on that."

Both moderates and conservatives have also questioned the wisdom of Coleman's decision, against the advice of some campaign experts, to ignore a Virginia tradition by not resigning from the attorney general's office to run for governor.

Campaign manager Anson Franklin heatedly denies Coleman is in trouble. He contends Coleman has accomplished all the major goals set for the campaign's preliminary period, including increasing Coleman's name identification, raising between $600,000 and $700,000 and establishing the candidate's image as an experienced, capable public official in contrast with relative newcomer Robb.

Coleman's critics concede none of Coleman's problems are politically fatal, especially this early in a contest both sides predict will be very close. But they say the problems have cost Coleman the momentum he had hoped to build easy on in order to whittle down the 10 to 12 point lead Robb has shown in polls commissioned by both campaigns.

"I'd like to say that Marshall won this preliminary round, but I'd be less than honest to call it anything other than a draw," says State GOP Chairman Alfred Cramer.

While Coleman's campaign has been perceived as faltering Robb's has been on an upswing. After a month of apparent dormacy, Robb emerged two weeks ago at the first debate between the two candidates and surprised virtually everyone with a forceful, issue-oriented presentation that stole the show from the usually self-confident Coleman. Robb then orchestrated a unity show at the Democratic convention here last weekend, avoiding open warfare with disgruntled party liberals while getting the conservative-to-moderate nominees he wanted as running mates for lieutenant governor and attorney general.

"Marshall with his transcending arrogance thought he would make short shrift of that little turkey and he got caught off guard," says one conservative GOP operative. Another party strategist contends the debate's net result may help Coleman because "it gave his campaign a badly needed dose of realism."

Franklin dismisses Robb's debate performance, saying "When you see a dog working on its hind legs, it's not a question of how well he walked but that he walked at all." But Coleman aides concede that relative harmony the Democrats showed in this resort city last weekend puts added pressure on them to pull off the same.

It won't be easy. The convention faces a potentially bloody showdown Saturday over the lieutenant governor's nomination between born-again New Right candidate Guy O. Farley of Warrenton, considered the front-runner, Holton-supported Rockingham Sen. Nathan Miller and Godwin-backed Newport News Sen. Herbert Bateman.

Coleman has declared "my active neutrality, publicly and privately," and so far has convinced members of all three rival camps that he means to stay out. But privately, many Coleman advisers say Farely could seriously damage the GOP ticket, fearful that his ties to TV evangelist Jerry Falwell will prove too controversial even for conservative Virginia voters.

There is little love lost between Farley's and Coleman's camp. Franklin and Farley campaign director John Alderson are longtime political enemies although neither cares to discuss their differences publicly. Many of the Farley people call Coleman arrogant, ruthless and far from a true conservative. Some of Coleman's supporters say Farley's people are, in Alderson's bemused phrase, "house-burners of the foam-in-the-mouth variety."

Perhaps an even more nagging problem for Coleman has been the lack of enthusiasm from a coalition of conservatives close to Godwin whose support -- and checkbooks -- have been a crucial element in the GOP's decade-long string of electoral victories in Virginia.

Coleman's support of the King veto won over some of these "Main Street" independents. "It was a $100,000 decision," says one Coleman insider, who says contributions began pouring in from the Main Streeters even though he contends money wasn't Coleman's motivation for the move.

Godwin held back on endorsing Coleman until today and his statement was a lukewarm one, disclosing his intention to support "the entire Virginia Republican ticket," but not mentioning the attorney general by name.

For now, Coleman's strategists are more concerned about having their candidate emerge from the convention without further alienation Republican regulars. They're so confident they can achieve that goal that at last Monday's meeting of the "Quiet Committee," the semiweekly gatherings of Coleman's campaign brain trust, only four minutes was allotted to convention preparations.