U.S. senator Dianne Feinstein has filmed an ad urging voters to vote against California's Proposition 8, the proposed constitutional amendment that would overturn the state supreme court's May decision legalizing gay marriage by banning same-sex couples from getting married.

No on 8 campaign staff announced the new ad during a conference call with reporters Tuesday, in which they also said their fund-raising totals had reached $32 million, giving them a narrow $1 million to $2 million lead over Prop. 8 supporters.

Patrick Guerriero, the No on 8 campaign director, called the response from LGBT activists and straight allies -- Democrats and Republicans, big donors and small -- "overwhelming."

"We've now received [money from] more than 53,000 donors who have given gifts of under $100," he said, "and we've more than doubled the number of donors in the first 20 days of October."

The ad from Senator Feinstein comes one month prior to the 30th anniversary of the murder of gay activist and San Francisco city supervisor Harvey Milk. Feinstein, who was president of the city's board of supervisors at the time, immediately became San Francisco's mayor when Milk and Mayor George Moscone were shot.

Feinstein, speaking directly to the camera, says:

"In my lifetime, I've seen discrimination. And I see it again in Proposition 8. Proposition 8 would be a terrible mistake for California. It changes our constitution. Eliminates fundamental rights. And treats people differently under the law.

"Proposition 8 is not about schools or our kids. It's about discrimination, and we must always say no to that. No matter how you feel about marriage, vote against discrimination.

"And vote no on 8."

Organizers of Tuesday's conference call said they had felt a momentum shift since a call two weeks ago when No on 8 was about $10 million down and losing the fight in public opinion polls. Guerriero said polls now invariably show the race is a dead heat between the two campaigns.

But they warned that an onslaught of activity from the opposition was on its way, with social conservatives initiating a $1 million match campaign Monday.

"We expect them to raise a quick couple of million dollars over the next couple of days for their final stretch drive, meaning the No on 8 campaign, and our friends and allies and supporters, have to ramp it up one more time to keep pace with them," he said.

Kate Kendell, executive director of the National Center for Lesbian Rights and a member of the No on 8 executive committee, noted the fierce overtones the battle had taken since evangelical leader Chuck Colson referred to the vote as "Armageddon" in a New York Times editorial and Family Research Council's Tony Perkins tagged it as more important than the presidential race.

As a lawyer who isn't typically involved in political campaigns, Kendell said the level of distortion by supporters of the ban was "not only dispiriting but shocking."

She also singled out a letter the opposition sent to Equality California donors, demanding that they withdraw support from No on 8 and contribute an equal amount of money to the Yes on 8 campaign.

"You just can't imagine that in almost any other campaign," she said, using the example of campaign officials for Sen. John McCain sending letters to Sen. Barack Obama's supporters demanding their support and threatening some sort of retribution if they failed to comply. "It's really pretty extraordinary."

Guerriero outlined three courses of action people could take in the next week to help defeat the initiative: donate money, volunteer, and talk to their friends, family, and neighbors about what's at stake with the vote.

He said the campaign needed to keep the pace of raising almost $1 million per day between now and the election. "Now we know that this is the most intense and the most expensive social issue campaign in the history of the country," he said.

No on 8 is also trying to fill 5,000 volunteer slots to help get out the vote on Election Day, and people who want to help can sign up on its website. The site also includes a template to help people e-mail letters to their friends and relatives about Proposition 8. (Kerry Eleveld, The Advocate)