EW YORK - When Roman Catholics vote in tomorrow's primaries, they will redraw a political dynamic Republicans don't much like to discuss: the persistent unease between the party's Catholic and evangelical Christian factions.
Texas Governor George W. Bush's appearance last month at Bob Jones University, a fundamentalist college in South Carolina that harbors anti-Catholic thought and teachings, has ripped the scar tissue from a wound that Republican leaders are trying to heal.
''The tension with the evangelicals is always there. We're not supposed to talk about it. It's supposed to go away if we don't mention it. But it is a lie to say that it isn't a problem,'' said William Donahue, a conservative Catholic who heads the Catholic League for Religious and Civil Rights here.
The Bob Jones controversy comes on the heels of the flap in Congress over the appointment of a House chaplain, with Democrats and some Catholic Republicans claiming that a Catholic priest was rejected for the post because the GOP wanted to appease its evangelical allies.
Catholic political fears ''are not at the surface; they are not even just beneath the surface, but they are not deep,'' said Republican pollster Frank Luntz. ''There has always been an uneasy alliance between fundamentalist and born-again Christians on one hand and religious Catholics on the other. They agree on so much and yet there is distrust there.''
In public calls for tolerance in recent days, Catholic political leaders have played down the rift. New York's Democratic senator, Daniel Patrick Moynihan, joined last week with the Republican governor, George Pataki, to call for removing religion from politics.
But Senator John McCain is counting on the possibility that Catholics here and in New England will express their resentment in the voting booth.
The usually unspoken distress of many Catholics in the Northeast at the influence of the Christian right in politics was most memorably voiced in recent years by Representative Peter King, a Long Island Republican who supports McCain.
''Instead of going for solid working people, people who work hard, are patriotic and put their kids through school - we are driving them away,'' King said in a 1996 debate in Congress. ''We're going to turn ourselves into a party of barefoot hillbillies who go to revival meetings.''
The McCain campaign is making thousands of phone calls to the Catholics of New York state, who constitute some 50 percent of the Republican electorate, reminding them that the senator has stood firm against anti-Catholic bigotry.
McCain appeared Friday night at Sacred Heart University in Fairfield, Conn., a suburb of New York, and got an enthusiastic welcome. In appearances on the ''Today'' show and ''Imus in the Morning'' radio show, McCain continued to lambaste Pat Robertson and Jerry Falwell, two leaders of the Christian right.
''I have no doubt the fight has helped us with Catholic voters,'' said McCain campaign manager Rick Davis. ''At its height we were up 16 percent in New York.''
''The Catholic vote is going to go to Senator McCain for a number of reasons,'' said King. ''Bob Jones University is one, but also because he represents their values of patriotism, character, integrity. That is what it is all about, a question of character: Are you willing to shake hands with bigots to get votes?''
Political professionals aren't so sure. Pollster John Zogby's surveys of New York showed the Catholic vote swinging wildly between Bush and McCain last week. Bush continues to enjoy the support of a majority of Catholic women, and it was in the hope of maintaining that gender gap that he has made McCain's record on breast cancer research the subject of negative advertising here. This weekend the battle shifted to upstate New York, which casts a formidable chunk of the Republican vote and has a higher percentage of Protestant voters.
McCain faces the risk of overplaying his hand. ''Catholics don't want to be singled out,'' said Luntz. ''It's in the privacy of their home that religion has an impact.''
Religion became a mixed blessing for the GOP when millions of Catholics and evangelical Protestants left the Democratic Party and flocked to the Republican banner in the last 30 years, giving Presidents Richard Nixon and Ronald Reagan victories and helping the party claim control of Congress.
A mutual distaste for Democratic liberalism, especially on social and family issues like abortion, gay rights, and the use of vouchers for religious schools, gave the Catholic and evangelical wings of the GOP something in common. So, too, in working class precincts of both the North and South, did economic issues like high taxes and affirmative action.
This month's St. Patrick's Day parades in New York and South Boston, which ban gay and lesbian groups, illustrate where Catholic conservatives share the views of evangelical Christians in opposing homosexuality.
The simmering antagonism between the two groups dates back to the Protestant Reformation; to ethnic rivalries between Catholic immigrants and Protestant elites in cities like Boston and New York; to the anti-Catholic crusades of the Ku Klux Klan; and to Protestant resistance to the presidential candidacies of Catholics Alfred E. Smith and John F. Kennedy.
Attitudinal and stylistic differences add to the unease. Bigoted Protestants view Roman Catholic doctrine as medieval idolatry, Donahue said, while their Catholic counterparts see Protestant fundamentalism as a ''bizarre'' backwoods tent religion.
In a general election, Catholics are one of the nation's premier political swing groups. In years of tracking the Catholic working class, pollster Stanley Greenburg has documented the Catholic flight from the Democratic Party. But each time it seemed that Catholics were ready to align themselves permanently with the GOP, Greenburg said, concerns about the influence of the party's extreme wing caused them to shy away.
As Italian, Irish and Polish Catholics have assimilated and grown more affluent over the years, religious differences have faded. The Catholic community generally laughs at lampoons of Catholic school days or sexual attitudes, and has shrugged off fundamentalist extremism.
''George Bush did it all when he went to that Bob Jones school ... that calls Catholics a Satanic cult and the church a threat to all and the pope a rat,'' wrote Newsday columnist Jimmy Breslin, tongue-in-cheek, last week. ''This requires that Catholics up here quell the inner fury and maintain moderation in the face of attacks by these cheap, grubby Southern swine.''
''We don't take it too seriously because it doesn't affect us at work or at school,'' said Donahue. ''Many Catholics don't want to confront the culture. They want to be liked. There is a latent insecurity among American Catholics. They want to keep ducking, to not rock the boat.''
But Donahue and others think that the latent resentment of Catholic voters will emerge tomorrow. ''The case of Bob Jones University will work on those who, though they were drawn to the Republicans by disaffection with the Democrats, were always uneasy,'' he said.
At least on the surface, McCain's appearance at Sacred Heart University seemed to prove the point. ''There is a lot of emotion running through the campaign right now,'' said student government president Jason Slattery, over the roar of the rally in the college gym.
''I think he's going to pick up a lot of Catholic votes, and a lot of the born-again Christians who are not as extreme as Falwell and his buddy in Virginia,'' said Mario Falsani, a Catholic in the crowd, referring to Robertson.
New York's bruising brand of ethnic politics offers fertile soil for such a controversy. ''McCain has pulled the pin on one of the biggest rhetorical grenades I've seen in a political campaign in generations, leaving George W. Bush on his knee before Catholic voters,'' said Mark Green, the New York City official, who is a Democrat. ''The Republican primary has turned into a religious war.''
