WASHINGTON — Images of protesters mobbing the National Mall and marching in other cities across the nation tend to grab the attention of any politician.
But unlike the civil rights demonstrations of the 1960s, which spotlighted racial injustice and spurred landmark changes in the law, Monday's immigration rallies may not have the outcome sought by advocates of a more welcoming approach to the contentious issue.
Although the demonstrations provided a rallying point for those who oppose the strict measures advocated by conservatives in Congress, many political analysts believed the protests could also reinforce the position of those demanding a hard-line approach to immigration policy.
Many of Monday's demonstrators were not citizens or voters, but Spanish-speaking legal residents and illegal immigrants. Their potential for mobilizing political support is not clear. Meantime, with most members of Congress at home testing the political waters during the spring recess and moderate Republicans facing a potential backlash from their party's base, some feared the protests could inflame tensions.
"They are having the opposite effect on voters in this country who are clearly wanting our borders secured and are uncomfortable with a worker program," said Rep. Michael K. Conaway (R-Texas), who supported the crackdown on illegal immigration approved by the House but opposes the provision of the bill that would make it a felony to be in the country illegally.
Conaway, whose West Texas district is 30% Latino, said more than seven in 10 constituents who responded to a survey backed a guest-worker program, but that many of those people expressed discomfort with earlier protests that seemed to feature the Mexican flag more prominently than the U.S. flag.
"It offends a lot of folks who are otherwise very rational people but have a great respect for law and order," Conaway said.
Ed Gillespie, the former Republican National Committee chairman who has organized businesses to back a guest-worker program and has cautioned conservatives in the GOP against alienating the growing Latino vote, expressed similar concerns.
"To a certain extent, they bolster those who want a border security-only approach, because many of them are illegal and are flouting U.S. law," he said.
But Gillespie said the effect could be mixed, suggesting that Republicans would be unwise to ignore demonstrations of such size and scope. "Many of them are very legal citizens, and that has to get the attention of a lot of policymakers who realize this is a very important issue to a big proportion of the electorate," he said.
Organizers of Monday's protests were clearly aware of the risks. Unlike previous gatherings, the rallies this time primarily featured U.S. flags.
Participants were led in the Pledge of Allegiance, and they responded to speeches by chanting, "USA, USA." Signs underscored the idea that many marchers were legal citizens, or at least planned to become legal: "Today we march, tomorrow we vote."
Still, though any solution on Capitol Hill will require bipartisan cooperation, the protests seemed much more aligned with the liberal Democratic base. The featured speaker in Washington was Sen. Edward M. Kennedy (D-Mass.), a liberal icon, and his Republican partner on immigration legislation, Sen. John McCain of Arizona, who is struggling to court conservatives for his anticipated 2008 presidential campaign.
Moreover, the protests were organized by immigrant rights groups and labor unions that are key to the liberal movement. And President Bush, a longtime advocate for open immigration laws who first proposed a guest-worker program in 2004, did not discuss the demonstrations Monday.
An e-mail to supporters from the centrist New Democrat Network, which focuses on Latino voters, described Monday's protests as a "direct refutation of the Republican Congress' reckless decision to prioritize politics over policy, in a desperate effort to shore up their faltering conservative base at the expense of our nation's broken immigration system."
Joe Garcia, a Miami-based strategist for the group, rejected the argument that Latinos and other immigration advocates should remain quiet. He said the protests reinforced a sense among many Latinos who voted for Bush that the rest of his party was not as friendly, particularly the House leaders who backed the felony provision for illegal immigrants.
"The Republicans are creating a Pete Wilson moment," Garcia said, referring to the former California Republican governor who backed Proposition 187 to cut off benefits to illegal immigrants.
The initiative was approved by a strong majority of the state's voters in 1994, though it was eventually overturned by a federal court. The active opposition to it, however, is seen as having helped turn California into a more reliably Democratic state.
Though the protests Monday showcased immigrants' contributions to American society, another key constituency watched from the sidelines: business.
Corporate lobbyists, also a component of the Republican base, favor a guest-worker program because businesses rely heavily on plentiful, low-cost immigrant labor.
Craig J. Regelbrugge, a lobbyist for the American Nursery and Landscape Assn. and a leading advocate for immigration overhaul, acknowledged that some could view the demonstrations with trepidation. The rallies, he said, could be "daunting to some people, perhaps threatening."
Still, he said, the TV images put a face on the issue, which he suggested could only help. "I'm inclined to see it as a net positive," he said.
But Regelbrugge added one dose of reality to sum up the discomfort that would probably linger with lawmakers when they returned to Washington.
"The preferred path for many in Congress," he said, "is to defer action."