In 1882, Congress passed and President Chester Arthur signed the Chinese Exclusion Act. Today we don't name laws as bluntly as we used to. But anti-immigrant sentiments are very much alive, this time expressed in opposition to the Comprehensive Immigration Reform Act of 2007.

For a certain kind of conservative, any attempt to grant a legal status to illegal immigrants is as welcome as salsa on their apple pie. One conservative commentator claims that the law is "going to erase America" -- an ambition even beyond Ted Kennedy's considerable powers. Another laments that "white America is in flight" -- and presumably not just to Jackson Hole or Nantucket for the summer.

At one level, any immigration debate concerns a raw political calculation: Who ends up with more voters? Conservative critics of the Senate bill argue that because most Latinos identify themselves as Democrats, a larger pool of American Latinos will mean that Republicans are voted into irrelevance. Most Republican political strategists respond: That is closer than you think. Given current demographic realities, Republicans cannot rely on their white base alone. If a Republican presidential candidate doesn't get about 40 percent of the Latino vote nationwide, he or she doesn't stand much of a chance on an electoral map where Florida and the Southwest figure prominently. A nativist party will cease to be a national party.

Breaking 40 percent is possible for Republicans. President Bush did it in 2004. Republican momentum among Hispanic voters has been strong in the past decade -- until Rep. Tom Tancredo and his allies began their conflict with the fastest-growing segment of the electorate.

Conceding Latinos to the Democrats in perpetuity is a stunning failure of political confidence. If the Republican Party cannot find ways to appeal to natural entrepreneurs, with strong family values, who are focused on education and social mobility, then the GOP is already dead.

But the real passion in this debate is not political, it is cultural -- a fear that American identity is being diluted by Latino migration. Tancredo is the lowbrow expression of this fear. Professor Samuel Huntington of Harvard University, whom Tancredo calls an intellectual mentor, presents the highbrow version. Huntington argues that Mexican migration is a threat to American unity and to the "core" of our cultural identity. "America," he says, "was created as a Protestant society just as and for some of the same reasons Pakistan and Israel were created as Muslim and Jewish societies in the 20th century."

There are many problems with this argument, not least of which is that about a fifth of Hispanics in America are Protestants, mostly evangelical Pentecostals and Baptists. Almost all of Bush's political gains among Hispanics have come from this group, which gave him 44 percent of their vote in 2000 and 56 percent in 2004. Hispanic Protestants tend to be conservative on social policy. And many conservatives, I'd be willing to bet, would feel more cultural affinity with Hispanic Baptists in their church pews than they would with Huntington's colleagues in the Harvard faculty lounge.

Yet these are precisely the people that Tancredo Republicans are alienating. Not all Hispanics view immigration favorably, but 100 percent resent being targets of suspicion. When I talked this week with the Rev. Samuel Rodriguez Jr., a prominent Hispanic evangelical, he said of congressional Republicans: "This is a party closing its door to us, hijacked by extremists."

"All I hear," he told me, "from conservative leaders I work with, very socially conservative people, is, 'I can't continue to vote for a party that is exposing threads of bigotry and racism.' " Conservatives need to be reminded that Latinos -- Protestant and Catholic -- are, in some ways, different from the mainstream culture. Higher percentages attend church regularly. Higher percentages of Latino immigrants are married; lower percentages are divorced. "The elephant in the room," says Rodriguez, "is the Latinoization of America. What are the results? America will be a more religious nation. America will continue to be a nation that promotes family values. Wow, that really turns American culture upside down."

For Rodriguez and others, religion adds an element beyond politics and culture to the immigration debate. The Christian faith teaches that our common humanity is more important than our nationality. That all of us, ultimately, are strangers in this world and brothers to the bone; and all in need of amnesty. This belief does not dictate certain policies in a piece of legislation, but it does forbid rage and national chauvinism. And this is worth a reminder as well.