Smeal was among leaders from six organizations that announced their endorsement of the Democratic presidential nominee at a news conference.
Obama also won the support of the National Organization for Women, which said it has not endorsed a candidate for president since Walter Mondale and Geraldine Ferraro shared the Democratic ticket in 1984. Ferraro was the first female major-party vice presidential candidate.
NOW backed New York Sen. Hillary Rodham Clinton in the primaries. "We join with her in saying 'no,'" said NOW President Kim Gandy, referring to a line Clinton used at the Democratic convention last month. "No way, no how, no McCain."
Gandy and Smeal dismissed polls that suggested McCain has received a boost in support from white women after he picked Palin.
"The die is not cast yet," Smeal said.
An Associated Press-GfK Poll of likely voters last week showed Obama's lead among women at 49 percent to 44 percent. The same AP-GfK poll showed that white women are backing McCain over Obama, 53 percent to 40 percent.
Gandy predicted women will quickly swing their support to Obama once they know where Palin stands on the issues. The Alaska governor opposes abortion except in the case of a threat to the mother's life.
However, data from the recent AP-GfK poll suggests that it might be difficult for Obama to win over some white women.
The survey, conducted Sept. 5-10, found 65 percent of working-class white women say Palin shares their values, 71 percent said so of McCain, compared to 52 percent for Obama and 46 percent for Democratic vice presidential nominee Joe Biden.
The McCain campaign said it was unhappy with NOW's decision to endorse Obama in the race for the White House.
"It's extremely disappointing that an organization that purports to be an advocate for all women not only opposes, but feels compelled to go out of its way to criticize and make negative comments, about the only ticket in the presidential race with a woman on the ticket," Palin's spokeswoman Maria Comella said in an e-mail.
Smeal said the organizations have and will continue to protest any sexism in the presidential campaign, but she added, "We think it's time to get off issues such as lipstick and on to the issues, really, that are challenging this nation."
Gandy criticized Republicans for changing their tone on sexism.
"I love it that Republicans have discovered sexism in the media," she said. "Because they didn't see any of it when it was being directed at Hillary Clinton. But once Sarah Palin got a dose of it, which we also pointed out, they were all over it." She did not explain how her group defended Palin from sexism.
Obama was also endorsed by leaders from Business and Professional Women/USA, the National Association of Social Workers, the National Congress of Black Women and the Women's Information Network.