A virtual who's who of the moderate wing of the Republican Party today led a march of 4,500 supporters of the Equal Rights Amendment through downton Detroit protesting the GOP platform's failure to support it.

"My party has endorsed the Equal Rights Amendment for 40 years," Jill Ruckelshaus, a longtime party activist and wife of one of the best known figures in the Nixon administration, declared in an impassioned speech at the end of the march. "Dwight Eisenhower endorsed ERA. Richard Nixon endorsed ERA. Gerald Ford endorsed the ERA.

"But something happened in Detroit last week," she bellowed, her voice cracking with emotion. "Give me back my party."

She was joined in the protest by Senate Minority Whip Ted Stevens (R-Alaska); Sen. Charles McC. Mathias (R-Md.); Sen. Jacob Javits (R-N.Y.); Rep. Paul McCloskey (R-Calif.), a 1972 antiwar presidential candidate; Rep. Margaret Heckler (R-Mass.); Helen Milliken, wife of the Michigan governor; Rep. Bill Green (R-N.Y.), and a host of local and state party leaders.

Helen Milliken wore a gold Republican elephant pin upside down. "He's in distress," she said.

The march, which passed by the site of the Republican National Convention as a sidewalk honky-tonk band played "I Want a Girl Just Like the Girl Who Married Dear Old Dad," was organized by the National Organization for Women. Most protesters were feminists and nonparty members.

But Republican moderates, upset over the rightward drift of the party, saw it as a vehicle to "send a message" to Reagan and the conservative forces who control the convention.

"This is a testimonial to something we believe strongly in," said Stevens.

"I think it's sending a message to the country that there are people in Detroit who support the Equal Rights Amendment," Mathias said. "It's a more important issue than it was 40 years ago because more women are in the work force and need protection."

The marchers stretched a half mile through downtown Detroit, tying up traffic and drawing occasional catcalls. "ERA Libbers. Read the Bible. Repent while there is still time," one anti-Era placard read.

The protesters played on a central theme -- that the GOP is throwing away millions of votes by turning its back on the amendment. They expressed their feelings in chants and placards: "Ratify ERA, Not Reagan," "Does GOP Mean Grand Old Pig?" "Will the party that freed the slaves enslave the women?" and "Reagan for Shah."

"I'm not sure Reagan's advisers understand the whole issue or the opportunity it offers them," said Doug Bailey, a respected Republican political consultant who joined the march. "The ERA is a litmus test issue. To a lot of young people a party that dismisses ERA is not going to get a hearing.

"Millions of Americans aren't particularly comfortable with Reagan but they hate Jimmy Carter. They're about ready to vote for Reagan if he just gives them a signal. He's missing it on ERA."

Reagan, he added, has two more opportunities to reach out to these groups -- his selection of a running mate and his nomination acceptance speech. Heckler said today that the furor over the ERA has increased chances Reagan will pick a moderate running mate.

"George Bush was pretty much out of it when I arrived here last week for the platform committee," she said. "But the ERA issue has cut so deeply I now think they are looking at George in a different light."

Just as the march and rally ended, the platform committee gave final approval to last week's drafted platform which acknowledges support and opposition to the ERA as "legitimate" points of view, but that the decision on ratifying ERA is "now in the hands of state legislatures."

Reagan has scheduled an hour-long meeting with leading ERA supporters for 10:30 a.m. Tuesday.

Meanwhile, another symbolic issue dividing moderates and conservatives emerged over the platform's judiciary plank, which put the party on record as supporting only judges who respect "the sanctity of innocent human life," that is, judges who oppose abortions."

Sen. Charles R Percy of Illinois, chairman of the 1960 platform committee, said he is trying to marshal enough support to eliminate the plank from the convention floor. Signatures of 27 platform committee members are necessary to bring up such a challenge.

Calling the plank "the most outrageous thing I have ever seen in a Republican platform," Percy said, "its design is the worst sort of extremism of the 1964 convention reincarnated. If you say every judge you pick has to be against abortion what's to stop from putting in a litmus test on ERA, gun control or anything else?

"This is a real test to see if we can get something like this out of the platform or if we're just here for a coronation," Percy added. "If moderate Republicans go home and feel they have been totally rebuffed I hate to think what's going to happen to the party."