Gov. John N. Dalton issued a sharp warning today to Virginia conservatives who want to back an independent gubernatorial candidate next year, predicting any such move would be futile.

While the Republican governor refused to predict which party would be hurt the most by a third candidate, the conventional opinion here has been that the GOP, which has captured the governor's office in three straight elections, stands to lose the most in a three way race.

"I have talked to several people . . . and I have told every one of them that I don't think a candidate running as an independent would do anything but muddy the water," said Dalton, who is expected to support Attorney General J. Marshall Coleman for the Republican nomination.

Dalton also invoked the name of the conservatives' most feared political bogeyman -- Norfolk populist Henry Howell -- warning that in a four-way race with Howell and a conservative both running as independents, the conservative could help elect Howell.

"I still think one of the major party candidates would be the winner, but you can't ever tell when Henry gets into it," Dalton said of the man he decisively defeated for governor in 1977. Howell himself said in an interview yesterday that he doubted the man the conservatives are considering -- State Sen. Elmon T. Gray -- will run, and added: "I certainly don't expect to run again."

Neither Coleman, the likely GOP nominee, no Lt. Gov. Charles S. Robb, the all-but certain Democratic choice, has impressed Virginia's Main Street conservative businessman who, until recently, dominated state politics. Buth Robb and Coleman, who classify themselves as moderate to conservative, have been viewed as too liberal and as outsiders by many of the Main Streeters.

As a result, some conservatives have launched a search for a third candidate. One leader of the search is said to be former governor Mills E. Godwin, who proved party labels were of little importance when he won a second term as governor running as a Republican in 1973, after winning his first term in 1965 as a Democrat. Godwin was not available for comment today.

The only name to have emerged so far is that of Gray, a Southside Virginia Democrat who has the conservative pedigree that Robb and Coleman lack. Gray is a millionarie lumberman whose father was a longtime state senator and chief lieutenant in the now-defunct Byrd machine.

Gray, who was also unavailable for comment today, has acknowledged that he is considering making a race, noting that "the people of Virginia may feel that now is the time to have a businessman as governor."

Gray's name came up four years ago as well, when conservatives who doubted Dalton's electability were looking for alternatives. But Howell's surprise victory over then-attorney general Andrew P. Miller in the Democratic primary proved to be a catalyst that brought almost all conservative elements into Dalton's camp, and Dalton went on to crush the former lieutenant governor.

Supporters of Coleman, who could be hurt the most by a Gray candidacy, are nonetheless sanguine. "Don't put any money on Elmon Gray," says one Coleman ally. "When people really get down to making some hard decisions next year they'll quikly realize that Gray doesn't have the name identificaton or the popular support to win."