Actually, the main street represented by their Chamber of Commerce want amnesty to save their worthless butts.
With amnesty, they will have a large, disposable and cheap labor force and an increased number of very dumb buyers.
This why the CC and their members have supported the inflow of cheap labor and dumb buyers, aka illegals for decades.
Of course, that's not who Palin meant by "Main Street" - maybe we need another street name to refer to working stiffs, neither Wall nor Main. (I'd like Evergreen Terrace, but I'm not sure it's a widely enough known reference.)