Immigrant rights supporters march through Phoenix. Demonstrators demanding a path to citizenship for an estimated 12 million illegal immigrants rallied Tuesday across the nation, hoping to spur Congress to act before the looming presidential primaries take over the political landscape.

Los Angeles ? Immigration rallies nationwide Tuesday produced only a fraction of the million-plus protesters who turned out last year, as fear about raids and frustration that the marches haven’t pushed Congress to pass reform kept many people at home.

In Los Angeles, where several hundred thousand turned out last year, about 25,000 attended a downtown rally, said police Capt. Andrew Smith, an incident commander. In Chicago, where more than 400,000 swarmed the streets a year earlier, police officials put initial estimates at 150,000.

Organizers said those who did march felt a sense of urgency to keep immigration reform from getting pushed to the back burner by the 2008 presidential elections.

“There’s no reason a pro-immigration bill can’t be passed. That’s one of the messages being sent today,” said Chicago protester Shaun Harkin, 34, of Northern Ireland, who has lived in the United States as a legal resident for 15 years.

Melissa Woo, a 22-year-old American citizen who immigrated from South Korea, carried a Korean flag over her shoulder in Chicago as she criticized politicians for “buckling at the knees.”

“Us immigrants aren’t pieces of trash, we’re human beings,” she said.

Protests were mostly peaceful, except for an evening rally at a park in Los Angeles, where some suspected of throwing rocks and bottles at police were arrested. Police fired rubber bullets and used batons to push the crowd out of the street and onto the sidewalk. It was not immediately known if anyone was injured.

Organizers had long predicted lower turnouts for this year’s marches, saying an increase in immigration raids in recent months have left many immigrants afraid to speak out in public. That’s a change since rallies in 2006, when some illegal immigrants wore T-shirts saying “I’m illegal. So what?”

Others believe that the marches have not pushed Congress to pass immigration legislation, and many groups are now focusing on citizenship and voter registration drives instead of street demonstrations.

Organizers said smaller crowds do not mean the movement to win a path to citizenship for 12 million illegal immigrants has lost momentum.

“People are saying we need to get together to demonstrate unity,” said Joshua Hoyt, executive director of the Illinois Coalition for Immigrant and Refugee Rights. “But with so much happening, and so many concrete victories, you couldn’t say the movement is weakening.”

After last year’s marches, the Senate passed a sweeping bill that would have provided a path to citizenship for many of the nation’s 12 million illegal immigrants. But the bill was never reconciled with the then-Republican-controlled House, and legislation has languished since last summer. Subsequent bipartisan proposals have gotten more conservative.

Democratic Party Chairman Howard Dean told immigrant supporters in Miami that a reform bill currently before Congress was “insane” because it would require many illegal immigrants to return home before applying for citizenship.

At one of several activities in New York, about 1,000 immigrants rallied at Washington Square park. They and their supporters added names to a painting of a tree meant to symbolize the American family and the crucial role of immigrants in U.S. history. People in the crowd then attached leaves containing names of family members to the tree.

“These people are hard-working people,” said Djounedou Titi, a West African immigrant who has lived in the U.S. for eight years. “They deserve credit. And the only credit this country can give to them is citizenship.”