A Latino movement? Or just a moment?

The turnout surprised everyone. More than 500,000 Latino protesters in Los Angeles last month. Nearly as many in Dallas Sunday. On Monday, hundreds of thousands nationwide. It's big, it's unprecedented - and no one knows what it portends.

Quite unexpectedly, a population living in the shadows of American society has emerged into full view and found its voice. Illegal immigrants and their supporters are on the march, galvanized by a House immigration bill heavy on enforcement and offering no path to citizenship.

Most of the protesters are Latinos. And for many, this is their first American political experience - the largest showing of such power from a group that has overtaken African-Americans in number.

The demonstrators identify with the civil rights marches of the '60s, singing "We Shall Overcome" in Spanish. They talk about the beginning of a national movement. "Today, we march; tomorrow, we vote," enthused, young faces chanted. On May 1, they plan a national boycott of jobs and commerce.

But is this a movement in the making or just a moment ?

It's a stretch to compare the protests to the civil rights movement. That struggle emerged from an entirely different history, including slavery and decades of statutory discrimination that took years of court and legislative action to overturn. What Congress is grappling with is more of a policy decision - a complex one, but a regulatory one nonetheless.

At the same time, the civil rights movement benefited from strong leadership. The Latino protesters are a grass-roots phenomenon, spurred on by Spanish-language media, and loosely organized. Churches, unions, and community groups, seeing this wave coming, have grabbed their surfboards and are riding it.

Nor is this the only Latino wave. A poll by the Pew Hispanic Center last August shows one-third of Latinos born in the US believe illegal immigration hurts the economy by driving down wages. About 60 percent favor banning driver's licenses for illegals.

At this point, the demonstrators' message also registers more as a protest against the specifics of a certain bill, than an agreed agenda on how to get to their goal of citizenship. If that goal is ever reached, is that the movement's end? Latinos, to date, have coalesced around single issues, but haven't shown much political unity on the national level. In 2004, they accounted for only 8 percent of the vote. Illegal migrants, of course, can't vote.

Which is another reason why it's so hard to gauge the protesters' influence on Congress. One sympathetic sentiment - "we are not criminals" - is apparently being heard. Wisconsin Rep. Jim Sensenbrenner, the Republican who sponsored the House bill, described as "overkill" the provision that makes it a felony to be an illegal immigrant or to assist one.

Yet many politicians are rightly standing firm for stronger enforcement of the law. And protesters may find they spark a backlash in advocating citizen rights for lawbreakers.

At this early stage, it's impossible to say where this new Latino movement, if that's what it turns out to be, is headed. It's fighting for more than 11 million illegal migrants. It wants its voice heard. For now, that's all that can be known.