Let me add my own two cents’ worth to the discussion Jonathan has started on the similarities and differences between these two topics. As I suggested the other day, my principal concern with amnesty, a guest-worker program, and increased legal immigration is not that it will tend to reduce wages for unskilled work to the minimum wage. I think these policies will tend to have that effect, but I don’t object to other policies that move low-end wages downward (such as the abolition of the minimum wage).
One point of agreement in this discussion seems to be that citizenship and voting rights should be withheld from guest workers, even if their terms of employment are renewed again and again. I just think that the idea of a permanent bloc of people in this country who have no political rights is a) disturbing if possible and b) more likely to turn out to be a conservative fantasy.
Finally, I would say that if the immigration proposals were merely economic in their impact I would probably support them. But a nation is (or should be) a culture as well as an economy, its generation of a shared sense of belonging is something that its people legitimately want, assimilation is necessary for that to occur, and high levels of immigration (legal and illegal) make that harder.