WASHINGTON — Senator Clinton will face a key test of support within the Democratic Party’s activist wing today when she addresses an influential group that was hostile to her a year ago and yesterday greeted her top rivals with loud ovations.

Mrs. Clinton will speak to an audience of 3,000 this morning as part of the “Take Back America” Conference, an annual gathering of liberal activists, where last year she faced boos for her stance on the Iraq war.

The New York senator and presidential hopeful has since taken a considerably more aggressive position against the conflict, voting against an emergency funding bill and calling for Congress to deauthorize the war. Those moves are likely to draw a more favorable reception today, but it may not compare to the cheers given yesterday to Senator Obama of Illinois and a former senator and vice-presidential candidate, John Edwards.

Messrs. Obama and Edwards each upped their rhetoric on the war, seeking to distance themselves from Mrs. Clinton even without mentioning her name.

“No more pontificating. No more vacillating. No more triangulating,” Mr. Edwards told the crowd at the Washington Hilton. “No more broken promises. No more pats on the head. No more we’ll get around to it next time. No more taking half a loaf. No more tomorrow. For the men and women who are leaving this country to serve in Iraq, there is no tomorrow.”

The North Carolinian, who has apologizing for his initial support of the war, has criticized Congress for not pressing to cut off funding for the war.

Mr. Obama reminded the audience that he opposed the war from the beginning, saying it “should’ve never been authorized and never been waged. “So many of us knew this back then, even when it wasn’t popular to say so,” Mr. Obama said.

Speaking passionately and with his voice often rising, the Illinois senator drew applause from the crowd several times. The response was even louder than for Mr. Edwards, who has sought to outflank his rivals on the left.

Mrs. Clinton addressed the war at an earlier campaign appearance yesterday, telling the American Federation of State, County, and Municipal Employees that while she saw a need for keeping residual forces in the country, there would be “no permanent bases, no permanent occupation.”

She also took a swipe at Mayor Giuliani when asked to respond to the Republican candidate’s recent statement that he would be willing to send more troops to Iraq if needed. “I don’t know where he thinks he is going to get the troops. Our military is stretched thin,” Mrs. Clinton said, speaking to a Democratic audience that booed the very mention of Mr. Giuliani’s name.

In addition to the leading Democratic candidates, the three-day conference, organized by the Campaign for America’s Future, features a list of speakers that reaches from the party’s mainstream to the fringes of the political spectrum. Among those on the program are House Speaker Pelosi, the chairman of the Democratic Party, Howard Dean, and Robert Fertik, the founder of a political action committee aimed at building support for the impeachment of President Bush and Vice President Cheney.

A spokesman for the conference organizers, Toby Chaudhuri, praised Mrs. Clinton for coming around on the war and other issues, but kept the pressure on in advance of her speech today. “This is a time to run with the wind, rather than tack,” he said.

Earlier yesterday, the other Democratic contenders addressed about 2,000 members of AFSME at a candidate forum across town from the conference. The leading hopefuls all voiced support for a congressional bill aimed at making it easier to employees to join unions. The legislation, known as the Employee Free Choice Act, has passed the House but faces a tougher road in the Senate, where the Democratic leadership expects to bring it to a vote within the next week.

The bill has drawn fervent opposition from some quarters, including the Center for Union Facts, a group formed to combat such legislation, which has assailed union leaders for opposing secret-ballot elections. The group ran a full-page advertisement in major newspapers picturing a prominent union president, Bruce Raynor, next to Idi Amin and President Ahmadinejad of Iran. Mrs. Clinton said yesterday that the “balance is out of whack” with regard to labor relations and that power had tilted too far to management, leading to intimidation and abuse.

“I’m all for secret ballots. I’m all for elections,” she said. “But then you’re going to have to have a lot more enforcement and supervision over what happens during an organizing drive than the current administration has been willing to provide.”

A Democratic colleague, Senator Kennedy of Massachusetts, was much more demonstrative at a Capitol Hill rally yesterday. Holding up a copy of the ad, he shouted, “This is what I say to them” before tearing the newspaper in half and throwing it to the ground.