The fuse for this week's massive immigration protests was lit in December, when Republicans in Washington, D.C., looking ahead to this fall's midterm elections, pushed a bill through the House of Representatives that party hardliners figured would help rally their base. As opposed to baiting antiwar liberals, as they did to great political effect during the 2002 midterms, or bashing gays, as they did to even greater political effect during the 2004 presidential race, this year Republicans planned to use the specter of illegal immigrants—taking your jobs, breaking the law, making a mockery of our border security—to lure red-minded voters to the polls.

The House immigration bill, which passed overwhelmingly on December 16 in the Republican-dominated chamber, would make being an illegal immigrant in the United States a felony, and would also make it a federal offense for any American to assist illegal immigrants—even so much as giving them food or water would be a crime. In addition, the House bill would require a large portion of the border between the U.S. and Mexico to be sealed off with a 700-mile, multilayer fence.

"For the first time, I can go out on the stump and say our party has done right on the issue of immigration," Rep. Tom Tancredo (R-Colorado), the fiery nativist who led the House push for the bill, told the Washington Post. "And I feel good about it."

However, rather than giving Republicans something to feel good about, the bill led directly to the giant marches of this week, including a Monday march in Seattle that Mayor Greg Nickels estimated at 25,000 people—a turnout that dwarfed some of the more recent antiwar marches in this city and brought unusual scenes of protesters waving American flags. The Seattle march and similar outpourings across the country show what can happen when partisans like Tancredo bet on the wrong wedge issue: a nation-wide backlash, and a huge political headache.

The current situation is partly a product of numbers. In 2002 there weren't enough antiwar protesters, much less enough sympathy for the antiwar position, to generate such a significant backlash against the Republican demonization machine. In 2004 there weren't enough out gay Americans to create the kind of mass protests pulled off this week in Los Angeles, Houston, Atlanta, New York, Seattle, and the nation's capital. But there are more than enough illegal immigrants in this country (11 million, according to recent estimates, with more than 500,000 arriving each year), and there is more than enough sympathy for their plight, to create a defining fight over immigration that Republicans are likely to regret for years to come.

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Moderate Republicans understand this, which is why people like Senator John McCain (R-Arizona) have pushed for legislation that would allow illegals currently residing in the U.S. to eventually become citizens. Even President Bush has supported this approach, proposing a "guest-worker" program in 2001. That idea, which went nowhere after the 9/11 attacks, would have allowed foreigners to work legally in the U.S. and could have granted "amnesty" to illegal workers already here. It also could have allowed for guest workers to eventually become citizens.

Part of the calculus that brought Bush and McCain to such immigrant-friendly positions is the desire to lure more Hispanic voters into the Republican Party. Hispanic Americans make up the largest minority group in this country, and the fastest growing. They don't vote in huge numbers now—while Hispanics account for about 14 percent of the general population, they made up only about 8 percent of voters in the last presidential election—but they do make up a significant percentage of the population in some key swing states, and experts believe they will vote in increasing numbers in the future.

For forward-looking moderates in the Republican Party, what happened this week is therefore a nightmare: The younger generation of Hispanic Americans saw their parents marching in the streets against Republicans. As adult voters, these young people are unlikely to forget which party vehemently opposed their family's presence in this country.

It's true that recently an increasing number of Hispanic voters have been casting their lot with the Republicans, largely in response to the party's focus on "family values." From 1996 to 2004, the Republican share of Hispanic voters doubled, from 20 to 40 percent. But that can change quickly, particularly if Democrats use the standoff over immigration to "show Hispanics who their real friends are," as Senator Charles Schumer (D-New York) put it in the New York Times last month.

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This sense that Hispanics are natural allies of the Democrats, and vice versa, is why Mayor Nickels, looking out over the massive crowd gathered at Westlake Plaza on Monday, greeted Seattle's marchers with "Hola!" and then told them: "All we see are Americans to the horizon." His speech received resounding cheers, with some of the shouts coming in a second wave as his words were translated for the non-English speakers in the crowd. There are an estimated 250,000 illegal immigrants in Washington, many working as agricultural laborers in the eastern part of the state; during a roll call of Washington cities, huge cheers went up at the mention of Yakima, Walla Walla, and Spokane.

In New York, on the same day, Senator Hillary Rodham Clinton told protesters: "Your faces are the faces of America." And in Washington, D.C., Senator Ted Kennedy (D-Massachusetts) invoked Martin Luther King Jr.'s famous "Let freedom ring" refrain, and told the tens of thousands of people gathered on the mall not far from where King gave his speech, "Some in Congress want to turn America away from its true spirit. They believe immigrants are criminals. That's false."

Tellingly, no Republicans spoke at the D.C. protest. Some may yet try to distance themselves from the more xenophobic elements of their party, but it's going to be hard to undo the impression, pounded home by the right-wing media machine, that Republicans are irredeemably anti-immigrant. On Fox News, anchor Brit Hume called the marchers "a repellent spectacle" and another commentator asked, "Is this the perfect time to round up these lawbreakers and ship them out?" Michelle Malkin, on her blog, referred to the protests as an "insurrection."

In the Senate, Kennedy and McCain are promoting a less punitive immigration bill, currently stalled, that would institute a guest-worker program and offer the millions of illegal immigrants already in this country a path toward becoming citizens—provided they pay a fine, learn English, hold a job, pass a criminal background check, and pay any back taxes. It's quite likely, however, that when the Senate reconvenes after Easter recess it will be unable to resolve the immigration issue.

Because of the protests—and recent polls showing broad support for letting illegals eventually become citizens—Democrats now have an incentive to take a hard line on protecting the Senate bill's current provisions from Republican amendments. Republicans, meanwhile, find themselves caught between the moderates' desire to court the Hispanic vote and the right-wingers' apparent belief that every election year requires some minority group to be sacrificed on the altar of the Republican base. That tension within the Republican Party is unlikely to produce a bill that Senate Democrats can live with, and even if it does, House Republicans would probably never sign off. All of which could throw the immigration debate back into the state it has been in for years: unresolved limbo.

What can't be put back into its prior state, however, is the immigrant community, which now appears ready to take its demands to the street. It's a change that could revolutionize the immigration debate, and eventually force the U.S. government to finally address the fundamental collision of needs that has brought the issue to this breaking point.

"The U.S. needs our labor," one of the signs at the Seattle protest read. "We need our dignity." recommended

Kelsey Amble contributed to this piece.