Right now a lot of the Left comprises the "tree-huggers". We can get them on our side on this issue by making it about the environment.

I tried raising this tactic here before when I said it's a water rights issue. What I am getting at is America is over-crowded and cannot sustain the population we have.

See http://www.numbersusa.com/ for a starting point on this. Also http://www.susps.org/

America already does not have enough water for the people and animals who are here. Every additional illegal immigrant adds to that over-load. That over-load is destroying habitat and that endangers various species.

The argument is self-sustaining once the environmentalists get the idea. They will run with it and they are already organized.