DENVER -- Thousands of demonstrators staged election-year rallies across Colorado on Monday, urging Congress to grant legal status to some illegal immigrants and to protect their families from being broken up by deportations.

In Grand Junction, Boulder, Denver and Colorado Springs, marchers chanted and carried signs saying "We're workers, not criminals" and "No immigrants, no America." Some waved U.S. flags; one speaker draped a Mexican flag around her shoulders. Smaller rallies also were held in Telluride and Avon.

Denver police estimated that between 7,000 and 10,000 people attended a candlelight vigil there Monday evening for immigrants who lost their lives while trying to cross Mexico's border with the United States.

Grand Junction police estimated the crowd there at 3,500. Official estimates on the other rallies were not immediately available, but they appeared to draw between 150 and 500 people each.

Similar rallies in dozens of other cities around the country drew tens of thousands of people.

The demonstrations are sure to play a big role in Colorado's fall elections, energizing both sides of the immigration debate and likely prompting many inactive voters to register, political analysts said.

"It's certainly captured the political agenda at every level: municipal, state, Congress. It's on the agenda for keeps, I think," said Colorado State University political science professor John Straayer.

"For (anti-illegal immigration hard-liners), it's going to rigidify folks and make them even more angry. It will give a rallying cry and calling card to those on the other side, and a lot of Americans are getting an education along the way," Straayer said.

Legalization would prevent exploitation of illegal immigrants and raise minimum wages for all workers, said James Johnson, political director for the Service Employees International Union Local 105, which helped organized some of the rallies.

"Our hope is that the rallies will get the federal government to pass comprehensive immigration reform to provide secure borders, and by providing secure borders, it allows for portals for immigration into this country," said Johnson, who attended the rally in Grand Junction.

Rep. Tom Tancredo, a vocal advocate of cracking down on illegal immigration, said the demonstrators were trying to "demonize" those who favor secure borders.

"Today's rallies show how entrenched the illegal alien lobby has become over the last several years," said Tancredo, R-Colo.

"The iron triangle of illegal employers, foreign governments and groups like La Raza puts tremendous pressure on our elected officials to violate the desires of law-abiding Americans and to grant amnesty," he said in a written statement.

Polly Baca, a former state legislator and president of the Latin American Research and Service Agency, said the immigration system should be changed, but "in a way that is consistent with our American values of justice, family, equity and human dignity."

"What folks are recognizing is that the silent majority out there that is committed to basic American values is now standing up and saying no to the negative, no to the unfairness, no to those people who would harm others," Baca said.

At Sloans Lake in Denver late Monday, people listened to speakers, then walked around the body of water. Some carried candles or small wooden crosses with the names of those who had died trying to enter the United States. Some beat drums and chanted.

"I just think we need to show our government that they can't enforce policies that, in my opinion, are inhumane," said Yvette Larrea, who was with her 6-year-old daughter.

The Denver woman called immigration an international issue.

"I love Mexico, but Mexico needs to be involved taking care of its own people," Larrea said.

William Valenzuela, 29, came to the United States from Guatemala when he was 18. Though in the country legally, many of his family members are illegal immigrants. He said he worried they would have to leave if laws changed.

He said the majority of immigrants were hardworking people who pay taxes and follow the law.

"The opportunity we have here, we don't have in our country," he said as he walked around the lake with his wife and two small children.

In Boulder, University of Colorado senior Jazmin Chavez told the crowd, "You all who came over on the Mayflower broke laws, too."

"We are all immigrants," she said, the Mexican flag wrapped around her.

At Civic Center Park near the state Capitol in Denver, a crowd including many high school students listened to mostly Spanish-language speeches and chanted "Si se puede," or "Yes, we can," the motto of farm labor organizer Cesar Chavez.

Many said they heard about the rally at school by word of mouth or telephone text messages.

"We've got to stand up for what's right because this country is made up of immigrants," said Jose Juan Munoz, 14, a student at West Middle School in the eastern suburb of Aurora.

Munoz said he walked the 10 miles from his school to the park.

In Colorado Springs, demonstrators chanted "Legalization" and "We are workers, not delinquents," The Gazette reported on its Web site.

Johnson said the rallies were having an impact, because the Senate came close to passing a bill more palatable to immigrant advocates after a harsher version passed the House.

"The Senate actually started to listen to the voices of the people in the communities," he said.