A decade-long battle over the Equal Rights Amendment ends today with its winners and losers gathering here to celebrate.

Phyllis Schlafly, the anti-ERA leader, plans an "Over the Rainbow Celebration" at the Shoreham Hotel. The National Organization for Women has scheduled an "Until Justice is Ours Rally" in Lafayette Park at noon and has declared political war on ERA opponents, pledging to campaign in the fall against those who helped defeat it.

ERA-America, an umbrella group of pro-ERA organizations, plans a "Thank You" party for its supporters. Maureen Reagan, the president's daughter, is to give a speech at the National Press Club reaffirming her support for the amendment, which her father opposes.

Throughout, there will be plenty of Monday-morning quarterbacking as the winners and losers claim responsibility for victory and assign blame for defeat of the amendment that would have outlawed discrimination based on sex.

Passed by Congress in 1972, the ERA has been ratified by 35 states, three short of the 38 needed by today to become part of the Constitution. Congressional supporters intend to reintroduce the amendment July 14, thus starting the entire process over again.

The National Women's Political Caucus plans to release a "dirty dozen" list today of state legislative leaders it blames for the defeat of the ERA. Ten are Democrats, two Republican.

"We've been saying for years that a handful of men are responsible for killing ERA," said Kathy Wilson, president of the caucus. "We think it's time to make the names of these men household words."

Meanwhile, NOW intends to release a list of Republican legislators who voted against the amendment in recent months, and to lay out a strategy for attacking the GOP, which removed the ERA from its party platform in 1980. NOW issued a similar attack on the Democratic Party last Saturday.

ERA supporters and opponents see the day as highly symbolic. For the former, it is a day of recommitment; for the latter it is the day ERA dies. While opponents celebrate a funeral, supporters say they'll be celebrating a rebirth.

"I'm sad and a little bitter. I think we all need a little rest," Wilson said yesterday. "I think it's the beginning of the politicization of the women's movement. We've all decided it's time to quit trying to change hearts and minds and start changing faces."

As part of this effort, Wilson's group has launched a campaign to elect women state legislators. NOW hopes to put together a $3 million war chest to use in defeating ERA opponents this fall.

A host of conservatives, including Sens. Jesse Helms (R-N.C.) and Jeremiah Denton (R-Ala.), is scheduled to attend both Schlafly's celebration, a tribute to her emergence as a political force, and a seminar she is sponsoring Thursday.

Schlafly, president of Stop ERA, said she had decided to call it "Over the Rainbow" because "we've come through a storm and are looking for a bright new day."

"This is the end of ERA," she declared. "They just lost. The American public won't buy their product.

"They didn't have a product to sell. Their product wouldn't do any good for anyone," Schlafly added. "You could spend $1 million a day and not sell the proposition that women should be drafted."

Other ERA related events are scheduled around the country. ERA supporters in St. Paul, Minn., for example, plan to release hot-air balloons carrying the message "ERA is still afloat."

Another round of rallies, built around the theme, "A New Day Beyond the ERA," is scheduled for Thursday. The National Women's Conference Committee, a coalition of groups, is sponsoring a concert at Constitution Hall that evening.