When those in the shadows come out with verifiable proof they've been paid off-the-books without employers reporting them, without Congress applying an amnesty to those employers also, I can see a trainwreck for the both of them on the horizon.
That will come back to bite hard on the asses of those supposed-to-be pro-business GOPpers when their felon employer supporters begin having felony corruption charges thrown their way. Then when they ultimately lose both their big corporate doners and their most conservative base over the mess they cause from rushing into a half-assed "deal", it'll serve them right.
Not to worry. The number of illegals coming forward won't be enough to fill an Econoline van.