Her concerns were larger and more alarming. She noted that a troubling number of the non-Mexican illegal immigrants apprehended in 2004 were Afghans (in fact, they accounted for 57 out of 98,000 in 2004), and she warned that the gangland drug wars raging in Nuevo Laredo (nearly 400 miles away, on the other side of a heavily policed border) would soon be spilling over into Fort Worth. It was hard to say whether Granger was addressing local worries or fanning them, wrestling with real threats or creating fear. But one thing seemed certain: Like many Republican members of Congress, she intends to make illegal immigration a centerpiece of her campaign in the coming midterm election.

Indeed, the conventional wisdom in Washington holds that immigration is emerging as a pivotal issue in the 2006 elections. Some of the capital's most quoted columnists and pollsters say it is the topic to watch, not just in border states but anywhere, from the heartland to the Deep South, that has experienced an influx of newcomers. These pundits expect immigration to loom large in GOP primaries, with incumbents being challenged from the right, as well as in November between Republicans and Democrats.

And though Ken Mehlman, chairman of the Republican National Committee, has long been pressing in a different direction--struggling to shape a GOP more welcoming to minority voters--a bottom-up revolt is taking place within the party: a push to talk tough and crack down in the hope of appealing to the conservative base. It's no accident that Senate Majority Leader Bill Frist featured immigration and border security in his fall fundraising mail piece, or that the House's last act before disbanding for the holidays was to pass a bill calling for a fence along the border. The tough-talkers' hope: that immigration will be the GOP's new secret weapon, an emotional wedge issue to rally voters, pumping up turnout and helping Republicans hold on to threatened majorities in both houses of Congress.

The only problem is that neither public opinion research nor recent electoral history supports this hope. And Republicans planning to ride an anti-immigrant groundswell to victory do so at their peril--and the party's.

Of course, immigration is an increasingly pressing issue, both locally and nationwide. With some 1.5 million foreigners entering the country each year, more than a third of them illegally, voters are ever more concerned not just with the changes they observe, but also with a sense that the system is out of control--that minor irritants like loitering day laborers and Spanish heard in the supermarket will soon be growing exponentially. The issue appeals to a range of dark emotions: economic insecurities, fear of terrorism, and resentment about spending tax revenues on people who have no right to be here in the first place. Then there are the cultural concerns. According to Andrew Kohut of the Pew Research Center, some 40 percent of the public think the growing number of newcomers "threaten traditional American customs and values."

A chorus of restrictionist candidates, bloggers, and talk show hosts inflame these fears, and before long there is no separating the real from the exaggerated. Nor does it help, as some Democratic pundits point out gleefully, that Republican congressional candidates have little else to run on in 2006--few new domestic successes, a fresh batch of scandals, and not much else to distract from the war in Iraq.

Nevertheless, it is far from clear that any but a small minority of Americans care enough about immigration to vote on it. True, a recent Time survey found that nearly two-thirds of the public think illegal immigration is a serious problem, and according to a December Gallup poll, more than half would like to see the number of foreigners admitted each year reduced. It's also true that the "salience" of the issue--how important it is to people--has risen in the last year or so. Still, of eight major surveys that measured immigration's salience in recent months, none found it anywhere near the top of the list nationally.

According to both Time and the Rasmussen Reports, Iraq is nearly twice as pressing; according to the Wall Street Journal/NBC team, Iraq leads by a factor of three; and the bipartisan Battleground survey found that only 3 percent of voters felt immigration was "the Number One problem for the president and Congress," while Iraq was seven times more urgent and the economy four times. True, immigration can elicit strong feelings among voters, and a skilled politician can play on these feelings, raising the issue's salience. That's what campaigns are for. Even so, many of the best poll-watchers are skeptical that immigration will prove a magic bullet for Republicans. "It may be a big issue in a handful of contests," says Karlyn Bowman of the American Enterprise Institute, "but it's hard to see it having a broad impact in 2006. Only a small group of people is going to feel so intensely that it's going to determine who they vote for."

Recent history bears this out. Anti-immigration sentiment is a kind of fool's gold--apparently a winner, but invariably disappointing. Patrick Buchanan proved this big time when he ran for president in 2000, playing heavily on nativist fears and drawing less than 1 percent of the popular vote. Restrictionist activists claim they prevailed elsewhere that year, ousting incumbent senator Spencer Abraham of Michigan, who as chairman of the Senate Immigration Subcommittee had led a high-profile effort to increase visas for high-tech workers. But postelection polling showed that Abraham had been defeated from the left--a brilliant get-out-the-vote campaign by the Democratic party and the United Auto Workers--not the restrictionist right.

The truth is that no national election in recent decades has turned either way on immigration. Some half dozen challengers tried to use it last cycle, including in Republican primaries against incumbents on record in favor of a temporary worker program. One or two of these races were close: California congressman David Dreier, viciously targeted by local talk radio as a "political human sacrifice," had the worst scare. But all of the threatened incumbents survived, most of them handily.

Strategists expecting a tsunami this year say that things are different now, that anti-immigrant feeling is more widespread and more intense. But they were disappointed again last fall by the gubernatorial contest in Virginia and by a special election in southern California to replace departing congressman Christopher Cox. Virginia Republican Jerry Kilgore tried to ride immigration and a half dozen other wedge issues, from the death penalty to gay marriage, to the statehouse. Across the country, in California, third-party challenger Jim Gilchrist, founder of the volunteer border patrol Minuteman Project, played for higher stakes still, all but turning his race into a referendum on immigration. Both campaigns attracted national attention. The restrictionist movement pulled out all the stops: fundraising, blog endorsements, and what seemed like endless free TV time, courtesy of Lou Dobbs and Bill O'Reilly. Still, both candidates lost decisively (Kilgore took 46 percent of the vote, Gilchrist 25 percent), including among Republicans and in precincts where they had expected to win big.

The Virginia race in particular offered a glimpse of the promise and peril of immigration as an electoral issue. Kilgore wasn't wrong: His own polling and that of his opponent, Tim Kaine, showed the topic growing in importance for Virginia voters. And Kilgore's campaign--"What part of illegal does Tim Kaine not understand?"--succeeded in increasing its salience, particularly among Republicans. The pitch that played best, across the ideological spectrum, was Kilgore's complaint that Virginia was rewarding illegal behavior, using taxpayer dollars for benefits--cheap tuition, health care, day laborer hiring halls--for people who had no right to be in the state.

Still, concerned as they were about the substance of Kilgore's charge, many voters, both Republicans and independents, were troubled by the way he leveled it, seeming to exploit the issue without a credible solution. He never conceded that the booming Virginia economy might need some help from foreign workers, and his best answer to what most people grasp is a national problem was to deputize local cops. As California strategist Arnold Steinberg, active in the effort to stop Gilchrist, explains, "A wedge issue is an oxymoron--it only works if it isn't perceived as a wedge issue. If voters believe you are using an issue opportunistically--and believe me, they pick up on that immediately--they are repulsed by it and go the other way."

Kaine pollster Pete Brodnitz backs this up with numbers. Though the 70 percent of Virginia voters who thought immigration was the most important issue pulled the lever for Kilgore, he lost 2-to-1 among moderates turned off by his anti-immigrant rhetoric. He ran well behind Bush's record in suburban and exurban areas close to Washington. And asked the day before the balloting who they trusted more to handle immigration, voters split evenly between Kaine and Kilgore, with nearly a quarter still unsure, confused rather than enlightened by the divisive campaign. Meanwhile, not surprisingly, Kilgore also alienated Hispanics. Though only a third of Virginia Hispanics are Democrats--and as of May 2005 they were evenly divided about who should be governor--they had turned sharply against Kilgore by Election Day, voting 58-to-42 percent for his opponent.

No doubt a better candidate would have handled things better. Poll after poll shows that voters sense the complexity of the issue--that immigrant workers are good for the economy, and impose costs on American taxpayers; that national security is a real concern, and we can't just close the border; that unlawful behavior should not be rewarded, and we can't deport the estimated 11 million illegal immigrants already living in the United States. What's needed are candidates who can speak to this complexity and offer balanced, practical solutions. A recent survey of Republican voters conducted by the Tarrance Group for the Manhattan Institute bears this out: More than three-quarters of those polled favored a policy that combined much tougher border enforcement, much tougher penalties for employers who hired unauthorized workers, and a way for illegal immigrants to earn their way onto the right side of the law.

The bottom line: Immigration can perhaps be a winner in November, but not as a wedge issue designed to divide and agitate voters. Candidates face a choice: bashing immigrants or making a constructive effort to address the problem, and Republicans in particular will pay a price for getting it wrong. The cost among Latino voters, the fastest-growing bloc in the country, is obvious. (It's no accident that the California GOP has been unable to deliver a majority for a Republican presidential candidate since its 1994 decision to back the anti-immigrant ballot initiative Proposition 187.) But that will not be the end of it. An anti-immigrant crusade would alienate businesses, both those that employ immigrants and those that see them as potential customers. It would divide congressional candidates from the president and cloud his efforts to create a Reaganesque legacy of openness and optimism. And as in Virginia, it would alienate moderates, both in the party and undeclared. If all this isn't suicidal, surely it adds up to something close. Is the fool's gold that tempting?