Despite cold, gray winter weather and a seven-year history of defeat, several thousand supporters of the Equal Rights Amendment marched here today to demand that the legislature make Virginia the 36th state to ratify the measure.

The rally's labor union sponsors claimed nearly 8,000 participants, making it "the largest rally ever held in the state of Virginia for the ERA," according to march organizer Suzanne Kelly. That figures was more than double the 3.200 people who came for a similar protest two years ago.

Police put the estimate at a considerably lower 5,000. Still, said a capitol police spokesman. "It's one of the largest rallies we've had here in some time."

At least 50 chartered buses, some from as far away as Atlanta and New York City, descended on the city this morning. The demonstrators grouped at a park about a mile west of the capitol, then marched to Capitol Square, waving green, pro-ERA flags and carrying signs reading, "Wake up, Virginia," and "Equal Rights Now."

"We're the real silent majority," said Charlene Lowe of the Radford, Va., chapter of the National Organization for Women, who drove five hours to get here last night and carried her 12-month-old son, Clay, on her back. "If they just let us vote, you'd see a majority of Virginians are behind this."

The demonstrators played to an empty house. Most of the state's 140 legislators left here Friday for the weekend and are not due back until Monday morning. When they return they are expected to reject the amendment as they have done every year since 1973.

The ERA has gained ground in the state Senate, where the committee that must first approve the measure now boasts nine supporters among its 15 members. Some observers believe the proposal will even pass the full Senate, where it was defeated by one vote two years ago -- the only time in seven years that it reached the Senate floor.

But even the amendment's most staunch backers see no such success in the House of Delegates. ERA has been blocked for years by a 12-to-8 vote in the Privileges and Elections Committee -- whose majority is known as the Dirty Dozen by ERA supporters. This year the margin is likely to be 13 to 7 -- "the Thirteen Thieves," as one local wag has already dubbed them.

"frustration is the name of the game here," said Sonia Johnson, a Loudoun County housewife who leads Mormons for the ERA. "But that doesn't mean you don't give it a try. I believe in miracles -- and that's what it may take to get the ERA cut of that committee this time."

Johnson, who was drummed out of the Mormon Church recently, allegedly for backing the amendment, was one of more than a dozen speakers who addressed the crowd. Another was Joseph F. Lowery, president of the Southern Christian Leadership Conference.

Lowery told the crowd that "if Dr. Martin Luther King were alive, he would be here today in support of the Equal Rights Amendment."

He conceded that he and other civil rights leaders had not enthusiastically pushed for the ERA in the past, but pledged his future support. He said blacks, women and labor shared the same goals and the same enemies.

"If we want the 80's to be better than the 70's, we'd better get together and do it to them before they do it to us," said Lowery.

The demonstration was sponsored by Labor for Equal Rights, a coalition of state's labor groups that includes the AFL-CIO, United Mine Workers and the Virginia Education Association.There appeared to be nearly as many men as women in the crowd and a sizeable portion of blacks.

"I've been coming down here for five years, and it's the biggest crowd and the best mix I've ever seen," said a shivering Carol Pudliner of Arlington, president of the Virginia NOW group.

Pudliner spoke of NOW's hopes that the state Senate would approve the amendment, while nearby a guitarist exhorted a crowd with a reggae song whose key line was "the harder the battle seem, the sweeter the victory."