During the early years of his memorable time as archbishop of New York, John Cardinal O'Connor rarely lost an opportunity to protest the nation's abortion laws, and rather explicitly argued that Catholics ought to vote against pro-choice candidates, particularly if those candidates were themselves Catholic.

O'Connor's advocacy infuriated pro-choice liberals, not a few of whom suggested that the government challenge the archdiocese's tax-exempt status. Organizations like churches and other tax-exempt institutions are supposed to stay out of politics.

On Sunday, July 4, of this year, clergy from various denominations in Houston, Texas, used the occasion to advocate immigration reform in their Independence Day sermons.

This time, it was the right wing which was appalled, and once again, suggestions were made that the churches had forfeited their tax-exempt status.

It would seem clear that Americans resent clergy who mix politics and the pulpit, at least, that is, when they disagree with the clergy's position. Pro-life Catholics did not object to Cardinal O'Connor's homilies against abortion. Immigration reform advocates cheered the homilies of the Houston preachers who implicitly endorsed the Obama administration's new push to deal with the presence of 12 million illegal aliens (or undocumented workers, depending on your preference).

Separation of church and state is both a treasured tradition in America and a contested idea. Civil rights advocates in the 1960s, and anti-nuclear advocates in the 1980s, welcomed the support of clergy, many of whom marched in rallies and preached their politics from the pulpit.

Evangelical Protestants, of course, constitute a powerful political voting bloc and have supported one of their own, Pat Robertson, as a would-be presidential candidate.

So it would seem foolish and naive to suggest that somehow clergy and organized religion should play no role in public life. Yet that's the argument we hear now, in the debate over immigration as well as the debate over abortion. Neither right nor left has a coherent position on the subject.

And perhaps that is as it should be. If Americans really believed in complete separation of church and state, they would have muted the voices of Bishop John Hughes and the Rev. Martin Luther King and many others. Hughes, King, and other clergy were powerful advocates for their communities, and their voices were prominent in the political debates of their time. They spoke truth to power, and included in their message was a demand for social justice and fair play, to be achieved through political action.

The immigration debate has revived and certainly will continue to recycle arguments about the proper place of the clergy in political debates. The coordinated pro-reform sermons in Houston offered just a glimpse of the role which clerics and institutional religious bodies will play in the coming months as the White House, presumably, presses forward with new immigration policies.

The formative experience of the Catholic Church in the United States came in the 1830s and '40s, when immigrants from Ireland and Germany faced discrimination and outright hostility from native-born Protestants.

Anti-reform advocates, including the ancestors of that long-ago wave of immigration [past immigration surge-, object to what they see as the Third World washing ashore to bring down the power and might of the United States. It is painful beyond words to hear such sentiments from an Irish American, simply because those were precisely the sentiments which led to the Know-Nothing party in the 1850s and the revival of the Ku Klux Klan in the 1920s.

The Catholic Church hierarchy in the United States hasn't had much in the way of good publicity in recent years, but its stand on immigration reform deserves more credit than it will ever get.

The bishops see today's Mexicans, Nigerians, and Vietnamese as yesterday's Irish, Italians, and Poles, and they are acting in the spirit of Tyrone-born John Hughes, the leading cleric-politician of his day in the mid-19th century.

Hughes came to the defense of immigrants shunned by society. Today's bishops are doing the same, motivated not only out of concern for those who lived in society's shadow, but also out of a sense of solidarity. After all, hundreds of thousands of illegal immigrants worship in Catholic churches that once were home to Irish and Italian congregations.

The descendants of the Ellis Island generation may argue that their ancestors did it the "right way" – shuffling through the lines, answering the questions of government agents, submitting to cursory health examinations.

Today's illegal immigrants have done none of those things.

But, as the clerics of Houston reminded us, their lack of legal status should not blind us to their humanity. They did, after all, come here for many of the same reasons as the immigrants of old.

Can we put them on a path to citizenship and dignity while also establishing firmer control of our borders? The White House seems to think so. So do many Catholic bishops whose own families once were seen as too foreign, too alien, for mainstream American society.

The bishops may or may not be right. But surely they deserve to be heard.