Guest workers v. Illegals on worker wages

Dorgan said that "the main reason that big corporations want a guest worker program is that it will drive down U.S. wages." . . . .

Here is the puzzle. Democrats say that they are against a guest worker program because it will lower the wages of American workers. OK, fine, that is indeed the effect of letting in more workers. The puzzle is that the Democrats don't have any problem passing other laws that encourage more illegal immigration which would also reduce the wages of those same workers. To put it differently, making it harder for illegals to stay would also increase wages. It is interesting that the arguments regarding wages are only raised for guest workers and not the rest of the issues in the debate.