By Nurith Aizenman
Washington Post Staff Writer

Tens of thousands of immigrants and their supporters from across the United States packed the Mall on Sunday in a last-ditch effort to spur Congress and the White House to overhaul the nation's immigration system and offer its 10.8 million illegal immigrants a path to citizenship this year against increasingly long odds.

Warmed by occasional bursts of sunshine, the festive crowd beat drums and waved American flags and placards reading "Change takes Courage" and "Obama Don't Forget Your Promise!"

"We've been patient long enough. We've listened quietly. We've asked politely. We've turned the other cheek so many times our heads are spinning," Rep. Luis V. Gutierrez (D-Ill.), who has led the push for immigration legislation within the House of Representatives, shouted, to roars of approval. "It's time to let immigrants come out of the shadows into the light and for America to embrace them and protect them."

D.C. officials do not give crowd estimates, so it was difficult to determine whether turnout reached the several hundred thousand estimated by organizers. But the rally, which stretched from Seventh to 12th streets in a dense carpet of humanity, appeared to be the movement's largest show of strength since 2006, when mass rallies in favor of a legalization plan erupted in cities across the country.

As at past rallies by the movement, most of Sunday's participants appeared to be Latino, including many who broke into repeated chants in Spanish, such as "Sí, se puede!" (Yes, we can!) But there were also displays of diversity, including a group of Senagalese immigrant women, who had perched tiny American flags in their traditional headdresses, and immigrant Thai families carrying signs written in the script of their native country as they pushed their American-born children in strollers.

Like many in the crowd, 15-year-old Yessenia Saucedo, the U.S.-born child of Mexican immigrants living in Oakland, Calif., had spent weeks selling tamales and candy to raise money for the trip to Washington.

"It was important for me to come because my mother is undocumented, and we're constantly in fear that we're going to get separated," said the girl, who traveled for four days by bus with a group of youth leaders. "It's just very emotional for me to be here."

The roster of speakers also highlighted the degree to which immigrant-rights groups have broadened their coalition since their last major effort at a congressional overhaul of immigration failed in 2007.

Benjamin Jealous, executive director of the NAACP, was among the first to speak, underscoring recent widespread efforts by Latino leaders to reach out to a constituency often concerned that Latino immigrants take jobs from low-income African Americans.

Catholic leaders, who have long supported a legalization plan, were joined by evangelicals who have recently signed on to the effort.

Also onstage was Arlene Holt Baker, executive vice president of the AFL-CIO, which expressed reservations about the 2007 immigration bill, fearing that it did not protect workers' rights. This year, the union has united with others to back the effort.

Similarly, prominent Latino figures such as Janet Murguía, president of the National Council of La Raza, were joined by leaders of Asian American organizations and smaller groups representing immigrants from countries including Haiti.

Numerous speakers pointed to the political muscle Latinos demonstrated during the presidential election, when 57 percent voted for Barack Obama.

"Wake up and smell the cafecito!" yelled Maria Rodriguez, executive director of the Florida Immigrant Coalition. "Latino workers, campesinos [farm workers] and families are here to stay. To be counted in the ballot box."

Last week, organizers said the impending mobilization had already reaped results. In a commentary article in Friday's Washington Post, Sens. Charles E. Schumer (D-N.Y.) and Lindsey O. Graham (R-S.C.) laid out a blueprint for an overhaul bill. Among the points: Illegal immigrants would pay back taxes and perform community service before they could gain legal status, U.S. citizens and legal immigrants would be required to obtain a new high-tech Social Security card and a system to bring in temporary workers in line with the demands of the U.S. economy would be created.

President Obama, who appeared in a video message played at the demonstration, immediately endorsed the plan, although he stopped short of earlier promises to move on a bill this year. Senate Majority Leader Harry M. Reid (D-Nev.) also promised floor time if the bill emerges from the Judiciary Committee.

However, Sunday's rally also highlighted the challenges of taking on the immigration system with midterm elections approaching in the fall and at a time of 10 percent unemployment. Noticeably absent were business groups, such as the U.S. Chamber of Commerce, which was a key backer of the 2007 legislation. The chamber has expressed doubts about details of this year's proposal.

Despite the enormous showing just steps from the U.S. Capitol, much of official Washington's attention was focused on the action inside the building, where members of the House of Representatives debated in advance of the night's decisive health-care vote.

If, as was expected late Sunday, Democrats enact the measure using procedures that bypass Republican votes, many Republicans, including Graham, have vowed not to cooperate on immigration legislation.

"The first casualty of the Democratic health-care bill will be immigration reform," Graham said in a statement Friday.

Still, the mood of the crowd remained hopeful and often defiant.

"It really feels like we're finally being taken into account," said Rodolfo Amilca, 34, an illegal immigrant from El Salvador who lives in Silver Spring. "This is a day I will never forget. It was really special."