Del. C. Hardaway Marks (D-Hopewell) and other men on the House Privileges and Elections Committee smiled benevolently at Del. Dorothy McDiarmid (D-Fairfax) this morning when she asked them to approve the Equal Rights Amendment.

"I've got no problems with Dorothy McDiarmid," Marks had said before the hearing began. "She's precious."

Precious or not, the committee a few minutes later completed what has become a political ritual in Richmond: It killed the ERA bill, by a 12-to-7 vote, and virtually sealed its doom in Virginia on the eve of the measure's June 30 national ratification deadline.

The defeat was foreshadowed earlier this week when McDiarmid failed to get the full House of Delegates to allow the ERA bill to bypass the committee where it has died year after year, and come to a vote on the floor. For the past nine years, McDiarmid, 75, has been proposing the ERA to the Virginia legislature and lobbying her colleagues in the genteel, gracious manner that makes her a favorite in the male-dominated Capitol.

McDiarmid's charm and determination, however, have not been enough to overcome the ERA's biggest liabilities in Virginia: a divided organization, a well-funded opposition and what ERA backers say is the longstanding belief of male legislators that women are not to be taken seriously.

"I guess they prefer their women on pedestals," says McDiarmid, a senior Democrat who still remembers watching her mother march down Pennsylvania Avenue for women's suffrage in the early 1900s. Today's defeat, which national ERA proponents had expected, leaves the ERA three states short of the 38 needed for ratification. Amendment supporters say they will now concentrate their efforts in Florida, Oklahoma, Illinois, and North Carolina or Missouri.

To McDiarmid, banning sex discrimination through constitutional amendment is as important as the cause her mother championed. But legislators in conservative Virginia, which waited until 1964 to formally ratify the constitutional amendment granting women the vote, have had a host of reasons for opposing the measure.

Some say a public commitment to ERA could lose them votes at the polls. Just yesterday, an estimated 1,500 opponents of the measure came to the Capitol grounds for a day of lobbying and a rally capped with a recital by the Rev. Jerry Falwell's Liberty Baptist College band.

"My constituents oppose it," says Marks, explaining his vote. "I got a 15-to-1 response against it from ladies. If the women were completely solid on this issue, I could vote for it."

Others say that blue-jeaned ERA lobbyists such as Marianne Fowler of Alexandria have alienated more legislators than they have won. She was convicted in 1978 of assaulting a police officer and was physically carried from the Capitol after the House Privileges and Elections Committe narrowly defeated the ERA.

"You get so much more with sugar than you do with salt," says a member of the committee.

If some of the ERA lobbyists are criticized for being too tough, McDiarmid has run into criticism from some who say she is too much the lady and too little the log-roller. "You've got to have a disciplined approach rather than a 'Gee, we ought to do something about this' approach," said one Northern Virginia legislator who backs the ERA. "You've got to get in there and give them an elbow once in a while."

McDiarmid acknowledges that she hasn't played hardball politics on the issue. With the speaker of the House and the House majority leader lined up in the opposing camp, she says, the politics of gentility is a pragmatic strategy.

"One doesn't threaten what one can't deliver," says McDiarmid. "I can't beat them in their own districts, and I can't beat their programs in the appropriations committee . . . You don't wear brass knuckles if they're not real brass."

Certainly that approach has won McDiarmid widespread personal respect in the General Assembly. "She's a lady in the true sense of the word," says Del. Warren G. Stambaugh (D-Arlington). "She's gentle yet indomitable."

When McDiarmid recently came down with a mild case of pneumonia, Speaker A.L. Philpott indefinitely postponed consideration of a parliamentary proposal she had drafted to save the ERA. Then, when she returned, he allowed the matter to come up again--and the House killed her proposal 62 to 35.

Many proponents say there was little they could do to change the minds of Virginia legislators, most of whom campaigned against ERA. Says Del. Vincent F. Callahan (R-Fairfax), "Anybody who doesn't know how they're going to vote on that issue doesn't deserve to be down here."

ERA often got caught in the crossfire between the rival groups supporting it, ranging from the National Organization for Women to the Women's Political Caucus. Last month, one group pushed hard for former vice president Walter Mondale to lobby Virginia legislators--over the objections of the other group and Gov. Charles Robb.

But even that dispute wasn't as bad as in previous years. "It's amazing this year how friendly they've been to each other . . . ," McDiarmid says. "In previous years they weren't talking to one another at all."

With the measure roundly defeated in the House committee, the ERA's chances of ratification in Virginia are virtually nil. McDiarmid acknowledged from the outset that ERA's chances in Virginia were "very, very slim." Yet she still won't concede defeat.

"I suppose," she says, "one always hopes for miracles."