NEW YORK -- The national immigration debate is muddying Republican relations with Roman Catholics, swing voters who make up about one-quarter of the American electorate.
While Catholic bishops and many Republican politicians share opposition to abortion, they are often split over the specifics of immigration changes. Church leaders are challenging, and in some cases even vowing to defy, the tougher enforcement proposals by Republican lawmakers.
The issue highlights roadblocks that the Catholic view creates for Republicans and Democrats. Catholics are generally conservative on personal issues such as marriage, but tend to be liberal on social justice matters. This limits the appeal of both major parties, and leaves Catholics ''politically homeless," said the Rev. James L. Heft, president of the Institute of Advanced Catholic Studies at the University of Southern California.
''I'd like to see more prolife Democrats," Heft said, ''and social justice Republicans."
Immigration is not the first issue to split Republican and Catholic leaders.
Pope John Paul II opposed the US war on Iraq and the death penalty, for example.
But the latest differences have emerged only months before much of the Congress, which is now controlled by the Republicans is up for reelection.
The rifts also have arisen as the Republicans and Catholics had seemed closer than ever.
''Right now, a higher proportion of Catholic voters would identify with the Republican Party, or some of the themes that the Republican candidates have been using," said David Leege, a professor emeritus at the University of Notre Dame and a specialist on Catholics and politics.
But the impact of the immigration debate is unclear.
''The jury is out on the Catholic vote in long run," Leege said.
Catholics, who had once been perceived as solidly Democratic, have been moving toward the Republican Party for the past 25 years or so.
When Catholics established themselves financially, they started voting less according to religious ties and more according to economic interests.
The Democrats' support of abortion rights also drew them to GOP candidates.
President Bush, a Methodist, won the 2004 Catholic vote 52 percent to 47 percent over the Democratic nominee, John F. Kerry, who is a Roman Catholic.
Leading to the election, bishops had warned Catholic legislators that they risk ''cooperating in evil" if they vote for candidates supporting abortion rights.
Church leaders insisted that their position was nonpartisan.
Yet the timing of their statements was a boon to Republicans, since Kerry backs abortion rights.
But now, many of these same bishops are accusing GOP lawmakers of lacking compassion for illegal immigrants.
Archbishop Raymond Burke of St. Louis, who said in 2004 that he would refuse to give Holy Communion to Kerry for his expressed views, was among many church leaders who have organized rallies recently in favor of giving undocumented workers a chance at gaining citizenship in the United States. Many in the church are immigrants.
Burke also noted that the first American Catholics were immigrants themselves.
By welcoming migrants, Burke said, ''we obey the command of our Lord, who tells us that when we welcome the stranger, we welcome Christ himself."
Representative F. James Sensenbrenner, a Republican from Wisconsin, galvanized Catholic opposition by sponsoring legislation that the House passed in December that would make it a felony to be in the country illegally and making it a crime to help illegal immigrants.
Cardinal Roger Mahony of Los Angeles said his priests would disobey such a law.
Successive popes, including John Paul II, have stressed that countries with the resources to accommodate people fleeing persecution or hardship have a moral obligation to do so, regardless of legal status. About 30 percent of the nearly 65 million US Catholics are Hispanic, and the church has a service network for migrants.
Leonard Leo, the Republican National Committee's cochairman for Catholic outreach, said Bush ''has done a very good job of describing where the Republican Party ought to be on the issue, and I think that his vision is very consistent with where a lot of Catholics are."
Bush most recently lobbied for compromise legislation.
That measure would offer eventual citizenship to millions of illegal immigrants, while providing for stronger border security.
''The problem is that the term 'justice' is sometimes misconstrued to mean that we should basically disregard the law and provide whatever is viewed as the charitable solution," Leo said. ''The immigration area is a lot more complicated than that."