As President Obama's motorcade knifed through Seattle on Thursday afternoon, it passed a woman sitting on the grass, a baby on her lap. She held up a yellow posterboard with a message spelled out in black marker: "Thank You! Mr. President for standing up for my Mommys."

It was a powerful reminder of the symbolic weight of Obama's declaration of support for same-sex marriage last week, a historic political embrace of the cause of gay rights. By all indications, the move fired up the liberal base of the Democratic Party, caused supporters of the president to open their checkbooks - and mobilized social-conservative opponents who view same-sex matrimony as an attack on traditional values.

"The truth is, it was a logical extension of what America is supposed to be," Obama said at a $15 million fund-raiser Thursday night in the Los Angeles home of actor George Clooney. "Are we a country that includes everybody and gives everybody a shot and treats everybody fairly?"

Yet for all the attention focused on Obama's "evolution" to full-fledged support of gay marriage, he took no action to expand civil rights for gay men and lesbians, pointedly leaving the question of how to define marriage up to each state.

"Does that 'evolution' by the president make us more equal? No," said Heather Cronk, managing director at GetEQUAL, a California-based group that presses for the rights of gay, lesbian, bisexual, and transgender people.

"It actually doesn't do anything," Cronk said. Make no mistake, Cronk was thrilled with the symbolism. But she said, "The disappointing part is that he devolved back to the states' rights argument - he didn't even talk about this as a civil rights issue."

Indeed, members of GetEQUAL picketed the White House on Thursday, the day after Obama endorsed marriage rights. They carried signs that thanked the president but said, "We still need employment protection."

It was a reference to a draft executive order that would ban federal contractors from discriminating against employees on the basis of their sexual orientation or gender identity. An estimated 22 million people would be covered by such an order. Obama has so far declined to sign it.

"This would make a concrete difference in people's lives," Cronk said.

Obama spoke out the day after voters in North Carolina overwhelmingly approved a constitutional amendment banning same-sex marriage or civil unions for gay people.

In November, referendums in Maine, Maryland, Minnesota, and Washington state will give those states' voters a chance to weigh in on gay marriage. Despite growing support for such unions in opinion polls over the last decade, opponents have won in all 32 states that have voted on the issue.

Earlier this year, the Democratic governors of Maryland and Washington signed laws permitting same-sex marriage, but opponents are already gathering signatures for ballot measures designed to forestall implementation of those laws; they are expected to qualify.

Maine voters repealed that state's gay-marriage law in 2009, but advocates have succeeded in getting a referendum question on the ballot to legalize same-sex marriage.

At the same time, the issue is working its way toward the Supreme Court. In February, a federal appeals court struck down California's Proposition 8, which bans gay marriage, as unconstitutional on grounds that it violates the 14th Amendment's guarantee of equal protection under the law.

In addition, gay-rights advocates are challenging the federal Defense of Marriage Act, which prohibits the federal government from recognizing same-sex spouses and says that states do not have to recognize same-sex marriages performed in other states where it is legal. The Obama administration said last year it would no longer defend the 1996 statute in court.

Meanwhile, a host of other gay-rights battles remain to be fought in state legislatures across the country. Ted Martin, executive director of Equality Pennsylvania, said he's not even thinking of pushing for marriage rights in Harrisburg. His group is hoping the legislature will move on bills prohibiting discrimination in employment and housing, as well as an anti-bullying program for schools.

"I don't want to downplay the announcement by the president that he's for marriage - it's so important - but we have a lot of ground to cover in Pennsylvania before we get there," Martin said.

Politically, Obama's stand energized each party's base, at least for the moment, bringing a fund-raising windfall.

"It was definitely a 'ka-ching' moment," said Larry Ceisler, a Democratic communications consultant in Philadelphia. "I must have [received] eight to 10 e-mails trying to raise money off this." They came from the Obama campaign, the Democratic National Committee, and various party committees, including those that support Houseand Senate candidates.

That the historic move could pose risks for Obama's reelection campaign almost goes without saying: It could peel away older, working-class voters in battleground states such as Virginia, Ohio, and Pennsylvania, Democratic strategists acknowledge. But neither Obama nor Republican Mitt Romney's campaign has much incentive to discuss social issues, given the dominance of the economy as the top concern of voters.

Polling shows the public about evenly split on same-sex marriage, and a USA/Today Gallup Poll released Friday found 51 percent approved of Obama's position. Yet 60 percent of registered voters surveyed said his change would make no difference in their vote.

"I think that this issue is close to a wash in terms of impact," said Chris Borick, pollster and political scientist at Muhlenberg College in Allentown. "It may energize a bit more support among young voters and progressives who had lost passion for Obama. The president's decision stirs some juices that have gone flat, and may get a few voters to the polls who could have sat this one out."

Borick said that the issue may make a few undecided voters "uncomfortable enough to move to the Romney camp."

Perhaps that was why Obama went no further, taking pains to say he was speaking "personally" and proposing no federal legislation. He is hardly doing a Lyndon Johnson - that is, throwing the full weight of his office behind an expansion of civil rights.

Even so, having a president for the first time embrace same-sex marriage, casting it in moral terms, is not insignificant.

"As of his announcement, favoring gay marriage is now fully, indisputably, and permanently a mainstream political position," said Jonathan Rauch, a guest scholar at the Brookings Institution who has written on the gay-marriage debate. "All hint of weirdness or stigma is gone."

More Coverage

Romney gives a forceful defense of conservative Christian values. A6.

Kevin Riordan: For presidents, and all of us, evolving takes time. B2.

Dick Polman: Obama's stance carries little risk. Currents, C1.

Contact Thomas Fitzgerald

at 215-854-2718 or tfitzgerald@ phillynews.com or on Twitter @tomfitzgerald. Read his blog, "The Big Tent," at www.philly.com/bigtent.