Running through and rejecting the standard arguments and claims (taking away American jobs, not paying taxes, being a drain on the healthcare system, etc.), which we know don't hold up, I would find that the Texas conservatives I talked to ended up mostly saying something vague along the lines of this: "well, we are here legally; and they ought to be here legally too." Of course, a response could then be to ask why amnesty - legalizing undocumented immigrants already in the US - isn't an option if legal status is the foundational concern. This then gets the whole cycle through the other claims/arguments going again. I wondered aloud, perhaps unfortunately even if in Socratic fashion, if racism isn't at the heart of the issue. Of course, few people are going to overtly argue that.
My colleague, Peter Levine, does a very nice job of summarizing the main stances for a "principled conservative" on immigration. I'm going to repost his post in its entirety because it's a very good one and difficult to chop up without losing the substance. But make sure you click through and check out some of his other posts.
On what grounds can a principled conservative oppose immigration?
One strain of modern conservatism is explicitly Christian and fundamentalist, in the specific sense that it uses the Bible as its "foundation." The New Testament seems a poor foundation for restrictions on immigration. The apostles are given the gift of tongues so that they may emigrate and convert everyone, everywhere. They show no respect for borders. "Then Peter opened his mouth, and said, Of a truth I perceive that God is no respecter of persons: But in every nation he that feareth him, and worketh righteousness, is accepted with him" (Acts 10:34-35).
Another strain is libertarian. Libertarians criticize the state for its use of force to restrain individual choice. They do not regard any state as intrinsically legitimate, but only as a tool for preserving liberty. Nothing could be more forceful than stationing agents with guns on a border to prevent individuals from moving freely across it. Immigration restrictions should be anathema to libertarians.
A third strain is free-market utilitarianism. The idea is that unrestricted markets are best for the most people--they are maximally efficient. That assumption should apply to labor markets as well as capital markets, and should therefore support free flow of people across borders. Possibly, it's good for the median US citizen to restrict the in-flow of poor people. But if we take utilitarianism seriously, it requires the most good for the most human beings--anywhere. If we are free-market utilitarians, we should favor free immigration.
A fourth strain is Burkean--skeptical about any radical changes, especially if they are engineered by law or regulation. On Burkean grounds, opening the US to massive immigration may have been a mistake in the 1960s, but reversing that policy would be equally foolish today.
A fifth strain is communitarian/traditionalist. The most attractive version of that philosophy says: Our community may not be better than anyone else's, but it gives our lives meaning and shapes our identities. We have the right to preserve its traditional outlines and to guide its growth. One might add that the traditional culture of some parts of America is English-speaking, Protestant, and of European origin (or of European and African origins). But that's no argument against immigration to New York City or LA, where the local traditions revolve around diversity and migration. Nor is it obvious that the real driver of cultural change in rural America is migration across national borders. Old ways would hardly be preserved if the newcomers were sent away.
Some conservatives have already decided that a few specific issues, such as abortion, have transcendent significance. It's not clear why they should also be opposed to immigration. In fact, new immigrants are less likely to favor abortion rights than native-born Americans are. Immigration may be a path to conservative social policy.
Finally, there's the idea of "rule of law." Actually, that's a complex idea with several components, but one element surely is the principle that a clear, written law must be obeyed and enforced. As some of the anti-immigrant activists ask, "What is it about 'illegal' that you don't understand?" I too am concerned whenever formal laws are massively disobeyed. This probably causes some loss of legitimate order and security; it also gives agents of the state too much discretion about when to enforce. But I'm not sure that rule of law is a specifically conservative principle. It is in tension with all the elements of modern conservatism listed above--and with many principles of modern progressive thought. I'd prefer to see it as a separate idea that has considerable merit when balanced against other values. (Of course, one way to respect the rule of law is to relax immigration regulations so that they are no longer widely disregarded by migrants and by American industry.)
I conclude that principled conservatives should not adopt an anti-immigrant posture. It's therefore disappointing the Republican presidential candidates should be united only by their opposition to immigration.