ANTONIO GONZALEZ is, ironically enough, delighted with Arizona's new law against illegal immigration. He is president of the Southwest Voter Registration Education Project (SVREP), which works to mobilise American Latinos as a political force. Its motto is su voto es su voz, your vote is your voice. The Latino movement usually grows by spurts in response to xenophobic overreactions by conservative America, and the Arizona law may be the biggest overreaction yet, according to Mr Gonzalez. It has “done more to organise our community than we could have done” and made it “the most vibrant social movement in America today, 100 times larger than the tea-party movement.”

Arizona's law, signed on April 23rd, makes illegal immigration a state misdemeanour in addition to a federal civil violation. It also requires local police, after making a “lawful contact”, to check the immigration status of people who cause “reasonable suspicion”, and to arrest them if they lack documents. To Mr Gonzalez the phrases “lawful contact” and “reasonable suspicion” allow cops selectively to pull over Hispanic-looking drivers like him on the pretext of a scratched windscreen or other trifle. The deputies of Sheriff Joe Arpaio in Maricopa County, which includes Phoenix, the state capital, are already notorious for doing this sort of thing, and the law would require cops to do it statewide.

And so a backlash has begun. Last weekend demonstrators protested in cities across the country, wearing T-shirts that said Todos somos Arizona, we are all Arizona. Liberal places such as San Francisco have threatened to boycott the state, and private companies have cancelled conferences there. Even Major League Baseball is considering relocating its 2011 All-Star Game, the first ever slated to be played in the state. To Arizona's conservative machos, this one hurts—especially since it recalls the National Football League's decision in 1991 to move the 1993 Super Bowl to punish Arizona for not making the birthday of Martin Luther King a holiday. (Arizonans then swiftly voted for MLK day.)

In the 1990s a similar backlash occurred in response to a Californian law, Proposition 187, approved by ballot in 1994 but blocked by the courts before it could go into effect. Supported by Pete Wilson, the Republican governor at the time, its objective was to keep illegal immigrants, most of whom were and are Hispanic, from using public services such as education and health care, and like the Arizona law, it required police to check up on suspects' immigration status. Instead, 187 galvanised Latinos, who registered to vote in record numbers and changed the politics of California permanently. Even Republicans now fear alienating them.

Latinos in other states, notably Texas, have also become more politically assertive. But those in Arizona appeared to be different until now. Many have been American for several generations, barely speak Spanish and are themselves ambivalent about the illegal immigrants coming through the Sonoran desert from Mexico, many of whom smuggle drugs or commit crimes. Just last week, there was another manhunt in the desert for illegal immigrants who had shot a sheriff's deputy.

But it now turns out that Arizonan Latinos are not different at all, says Arturo Vargas of the National Association of Latino Elected and Appointed Officials (NALEO), another Hispanic lobby. He worries that they are as reluctant as Latinos in California, Florida, Texas and New York to participate in this year's census because many of them fear that the information will be passed to immigration officials. This means that the population in these states could be undercounted, and the Arizona law has made that risk greater by increasing the disquiet. Simultaneously, though, Mr Vargas is encouraged to note that the law seems to have turned nearly every Latino citizen in Arizona into a lifelong voter.

But what does such mobilisation mean for America's politics? William Frey, a demographer at the Brookings Institution, a Washington, DC, think-tank, believes that Arizona may be a bellwether for the whole country in more ways than one. Over the past two decades Arizona's Latino population of children and young adults has grown so fast that the state now has what he calls the largest “cultural generation gap” in the country: 83% of Arizona's older people are white, but only 43% of its children now are. States like Nevada, California, Texas, New Mexico and Florida have gaps almost as large.

As a result, says Mr Frey, old white voters increasingly balk at paying taxes so that people they consider alien can go to school or the emergency room. The result, he thinks, is populist anger rather akin to that now fuelling the tea-party movement, which draws much of its support from white male baby-boomers. It is possible, says Mr Frey, that in Arizona the seeds of new racial and ethnic competition for public resources have been planted.

Polls seem to bear this out. One, by the New York Times/CBS News, suggests that 82% of Americans consider it either very or somewhat likely that the Arizona law would lead to people of certain racial groups being singled out. Yet slightly more than half of Americans also think that the law is about right, and another 9% think it “doesn't go far enough”. Our own YouGov poll (see chart) shows large majorities in favour of a range of enforcement measures. Within Arizona, people like Sheriff Arpaio, who has been re-elected four times, have soaring approval ratings. Mr Arpaio even thinks he could be elected governor (although he decided this week to content himself with remaining sheriff).

So instead of just one mobilisation, by Latinos, there may be two or more. And they could clash, pitting the old and white against the young and brown. Mr Gonzalez is sanguine about this risk. The marches of the past week have shown that many whites, blacks and Asians stand with Latinos in demanding more humane federal immigration policies. “Every American who doesn't want to see an apartheid Jim Crow society return will come to our side,” he predicts. Yet the other side produced protesters too, wearing T-shirts that said “Remember the Alamo”.