Virginia's chronically divided Democrats, still recuperating from a decade of nearly total defeat in statewide election contests, are being torn again.

The new dispute is over alleged efforts of conservatives to purge the party of liberal leaders.

The long-simmering feud became public today when former Lt. Gov. Henry Howell and his liberal allies threatened that some of their supporters might bolt from the party if two liberal Democartic National Committeemen from Virginia are replaced at the state party convention this weekend.

The immediate victim of such a split would be the Democratic presidential nominee, whose forces here would need a unified party to have any chance of capturing the state in November. In 1976, Virginia was the only southern state won by Gerald Ford and it is considered a likely Reagan stronghold this fall.

A longer term victim could be Lt. Gov. Charles S. Robb, the party's only statewide office holder and its likely gubernatorial nominee in 1981. Robb has refused to take a public position on the committee contest, but at least one of his staff members has been working for a conservative-backed candidate.

Robb in the past has alienated Howell-style liberals, whom many observers believe he needs, by not taking what they consider forceful stands on issues.

At the center of the fight is national committeeman George Rawlings, a crusty Fredericksburg lawyer who long ago alienated many party conservatives and moderates with both his politics and his abrasive personality.

Rawlings, the only major state party figure to back Sen. Edward M. Kennedy this year, warned today that if he and fellow liberal Ruth Harvey Charity of Danville lose their committee seats, some of their supporters "may not vote, or they may vote for (John) Anderson. sOr if they vote, they may not work in the campaigns."

Howell, who has lost three bids for governor, twice as an independent and in 1977 as the Democratic nominee, said Rawlings was a longtime political ally.

"If they drop him down the chute, it's a slap in my face too," said Howell, who warned that party conservatives were "trying to create a party in the image of Wat Abbitt (a legend and longtime Democratic congressman) and stamp out any liberal influence."

"That's ridiculous," retorted Richmond lawyer Angus H. Macaulay, a leader of the dump-Rawlings movement. "This is purely a matter of personalities and has nothing to do with political philosophy."

Macaulay especially bristled at Howell's warning that liberals might run a third-party gubernatorial candidate next year against Robb and Virginia Attorney General J. Marshall Coleman, the likely GOP nominee.

"This is a rule-or-ruin philosophy," said Macaulay. "Here's a man (Howell) who has run as an independent . . . and he has no right to talk about party loyalty because his record is miserable."

Howell released a three-page letter he fired off last weekend to state party chairman Richard J. Davis warning that the defeat of Rawlings and Charity would do "great damage" to the party.

Davis was unavailable for comment today, but his chief aide, Robert Watson, said, "If Dick felt there was a true purge of liberals or conservatives going on he'd try to stop it."

Watson said Davis was avoiding an endorsement of either committee slate, although party liberals have charged that the chairman has become part of the conservative movement to seize the reins of party power -- a charge Davis has denied.

Despite dominating the state legislature, Democrats have had a dismal record in statewide politics since 1966, the last time they won a U.S. Senate seat here. Since then, in a remarkable turnaround from the days when the party ruled Virginia, Democrats have lost three successive presidential and gubernatorial races and four straight Senate races. They now hold only four of 10 Virginia seats in the House of Representatives.

Many Democrats hope Robb, a relative newcomer to state politics, can reverse that record with a victory next year. But so far, Robb and Davis have appeared unable to mediate successfully between the party's warring factions.

A staff member close to both Robb and Davis, who is a likely candidate for lieutenant governor next year, said both men have virtually written off Rawlings and some of his supporters.

"Chuck knows they're not going to vote for him no matter what he does because, as far as they're concerned, he's not pure enough," the staff member said.Robb was out of town and unavailable for comment.

As for the major beneficiary of the squabbling among Democrats, a source close to likely GOP gubernatorial nominee Coleman said today, "God bless the Democrats -- aren't they wonderful."

George Gilliam, President Carter's state campaign chairman, said he was concerned that, if Carter is the nominee, the latest flap could cost his candidate votes in November. "The thing that is most important and hardest to gauge at this point is how well everybody comes together after the fighting is over," said Gilliam.