The labels liberal and progressive are often treated synonymously, but they are political philosophies with different origins and some differences in outlook that we might only recognize implicitly, if at all. Liberals and progressives are usually natural allies, and my intent here isn't to be divisive. But political differences can be clarified and even resolved if the underlying perspectives are made explicit and evaluated afresh in terms of specific issues, like immigration.
Historically, liberalism has been a political philosophy of the more humane members of the privileged and educated class, while progressivism has often been a product of life experience among working people and ethnic outcasts. With the democratization of education and blending of communities the distinction has softened, but the relative perspectives of what can be expressed in simple terms of (liberal) altruism and (progressive) pugnacity remain a real contrast with real influences.
Liberals tend to focus on altruistic political rights, whereas progressives tend to be more pugnaciously concerned with issues pertaining to living conditions - especially in the neighborhood and workplace. The question of illegal or unauthorized immigration is problematic for the usual sense of common cause between liberals and progressives mainly because it involves a conflict between a focus on rights for immigrants and the effects of immigration on citizens.
[Note: Illegal immigrant is an emotional label, charged with political implications, and often used as a pejorative by conservatives. Although it specifically and accurately applies to those who haven't entered the country legally, with a more sympathetic label, undocumented immigrant , the same people can be portrayed as those who are simply without ( legal ) documentation. Political affiliations and biases aside, the description undocumented obscures the reason people don't have documentation: they have crossed a national border without legal authorization. I prefer to use unauthorized as the more meaningful label, without prejudice or pejorative.]
Some positions on immigration as national policy are more strategic than philosophical. Leading Republicans use it as a wedge issue, a means of collecting support by inciting racism and fear. Some leading Democrats see the Latino/Hispanic vote as an electoral advantage to be gained by demonstrating compassion and support. Some union leaders seem to see the unauthorized as a pool of potential members and dues-payers to be organized. But my primary concern here is with principles of national policy, apart from consequent political and financial advantages or disadvantages.
There are some issues of national policy where I believe liberalism is better suited than progressivism to advance important principles. On freedom of speech, for example, the liberal principle of defending a nazi's or klansman's right to speak comes from what is arguably a clearer grasp on what is ultimately at stake in protecting everyone's rights. On unauthorized immigration though, I believe the progressive view is the better guide for promoting our national interest.
[Note: A concern for national policy and interests needn't be nationalistic . In a world of vast economic disparities between nations, uncontrolled immigration and trade serve to level differences by lowering working people's incomes to the "common denominator" rather than raising and protecting them. Unlike the conservatives, progressives and (in many ways) liberals favor national policies that foster improvements in conditions both here and in other nations, not increased advantages over others or decreased advantages for American workers.]
The liberal view on unauthorized immigration in its most abstract form is an expression of support for human rights, and compassion, and generosity toward the most abused and disadvantaged people in our society. Less clearly, less consciously perhaps, many appreciate the benefits of relations between the better-off and those who perform menial services. Progressives tend to have a more immediate involvement and experience with the effects of immigration policy. Their jobs may be at risk or may have already been lost by competition with immigrants, or their wages and working conditions and access to public services may be compromised. I believe it can be shown that many specific biases and opinions about unauthorized immigration flow from the differences in these general perspectives.
Perhaps because of an unfamiliarity with physical labor, many liberals tend to believe that immigrants are the only people who would be willing to perform the typical sorts of work they are doing. Progressives are more likely to recognize that the problem with difficult or unpleasant labor is the inadequacy of the wages unauthorized immigrants are compelled to accept, that citizens would consequently have to share.
I don't believe it can be stated too emphatically: Americans - brown black and white - are no less willing than immigrants to do hard work, if paid a living wage. It's also important to recognize that while unauthorized immigrants do many of the least favored jobs in our economy, they have been expanding into formerly unionized professions like skilled carpentry. It's not just about stooping and picking anymore, not even mostly.
The easy acceptance of false dogmas like those regarding the economics of immigrant labor is often an indication of disinterest, if not self-interest, in the difference between story and reality. With unauthorized immigration, when the concern for the rights of some is more interesting than a concern for the conditions of others, or when the enjoyment of a situation is more immediate and appealing than its confrontation, various supportive beliefs follow with partiality:
It's true, as it's widely believed, that immigrant labor has become indispensable to our economy. But in a larger, more comprehensive perspective, the displacement of national workers and collapse of wages is the reason immigrants have become indispensable. It's a national problem, a core problem, and a reversal of the trend, not its acceptance, is the better national solution.