Support for the Equal Rights Amendment which has long united Arlington's liberal Democrats in the conservative Virginia House of Delegates -- is fueling a bitter primary fight among the county's four incumbent delegates.

Women's political groups that supported all four delegates in past elections are funneling money and volunteers in Tuesday's Democratic primary solely to Del. Elise B. Heinz, whose Arlington-Alexandria floater seat has been abolished because of population losses in Washington's inner suburbs.

That abandonment has infuriated incumbents Mary A. Marshall, Warren G. Stambaugh and James F. Almand -- all ERA supporters who are scrambling to retain the three seats left to Arlington by reapportionment.

"I have felt very let down by the women's groups," says Marshall, a 60-year-old grandmother whose 13 years in the General Assembly make her the senior member of the county delegation. "They are having the same effect on me as any anti-ERA group."

Officials with Virginia's National Organization for Women and the Virginia Women's Political Caucus say their decision to support only Heinz, 46, a Harvard-educated lawyer who used to be an ERA lobbyist in Richmond, came after the three other incumbents announced they were running as a team.

"We told them when they were playing around with the idea of making a slate that, if they ganged up on Elise, we would have no choice but to support just her," says Marianne Fowler, chairperson of the Virginia Women's Political Caucus. "They have truly brought this situation down on their own heads."

For all the attention it has received in Northern Virginia, the ERA has never had enough support in Richmond to escape from the House Privileges and Elections Committee. But in the Washington suburbs campaigns have been won and lost over the issue.

The skirmish in Arlington has particularly pained Democratic officials there because the county's delegation to Richmond represents the party's last stronghold in Northern Virginia. For most of the past decade, both state senators and all four delegates sent by Arlington to the legislature have been Democrats.

During that same period, however, Republicans have been increasing their victories in the neighboring communities. The GOP has also gained control of Arlington's County Board and last year won the area's congressional seat from Arlington Democrat Joseph L. Fisher. On Tuesday the Republicans are conducting their own primary to nominate three challengers to the eventual Arlington survivors.

"The Republicans are very interested in these seats and if we get too divided over this, they could get some of them," said Sharon Davis, a Democratic party official, last spring.

When the 1980 census figures indicated that Arlington would lose its floater seat with Alexandria, the Democratic incumbents huddled to try and work out an amicable solution. Because Heinz' seat was the one to be sacrificed, the other three Arlington delegates suggested she withdraw and wait for a state judgeship or some other political opportunity to come along.

Heinz refused and Marshall, Stambaugh and Almand announced they would run together.

"It was not meant to be a ganging up type of thing on Elise," says Stambaugh, 37, who has been a member of the House since 1974. "It just seemed to us to be a safe course. . . to keep us from having this sort of donnybrook."

Neither Heinz nor the women's groups she used to lobby for in the General Assembly saw the wisdom of that solution. Heinz says she has received $850 from three women's groups and volunteers to staff phones and distribute literature.

The three remaining incumbents concede that Heinz has capitalized on her underdog role. But they claim groups like NOW and the Virginia Women's Political Caucus have hurt their cause by taking sides in the primary.

"I think it's regrettable that the money and effort of the women's groups didn't go in races where there are candidates who don't support women's rights and the ERA specifically," says Almand, a former prosecutor who was elected to the House in 1978, the same year as Heinz.

Fowler, who calls Marshall, Stambaugh and Almand the Gang of Three, says her organization's efforts in Arlington are justified because Heinz "is the original and ongoing leadership of this ERA movement."

Because Almand finished behind Marshall and Stambaugh in the last two elections, his seat appears the most vulnerable. But the 32-year-old lawyer says he is not running scared. He has the support of the courthouse crowd and local tenant organizations whose cause he has championed.

Stambaugh, who has led efforts to repeal the state's 4 percent food tax and is considered by many to be the county's most visible delegate, did not sound overconfident this week.

"I'm always paranoid about elections," said Stambaugh who fears the turnout on Tuesday will be extremely low because of the confusion over the state's redistricting plan, the Republican primary on the same day and the traditional apathy Arlington voters have shown for primaries.

"The last time we had a primary that had only one race on the ballot was in 1979. We go about 4,700 peopleto vote," said Stambaugh.

"We're right in the middle of it," says Heinz. "It's very hard for us to appreciate how unimportant most Arlingtonians think we are."

Four Republicans are running for three nominations in Tuesday's Republican primary. Theodore A. Lattanzio, 34, a deputy director of the National Rifle Association, sought a House seat in 1979. E. J. Jarvis, 37, a life insurance underwriter is considered by many Republicans to be the strongest candidate.

The remaining two candidates are Georgia A. Delyannis, 48, who has worked for her husband's engineering firm and Michael H. Steinmetz, 23, a legislative assistant for the Public Service Research Council.