According to the Census Bureau, during the 1990's, the illegal immigrant population grew by about half a million per year. That was mostly during the Clinton administration.
I have long believed that liberal Democrats, seeing the hold on the South that Republicans have, are flooding this nation with illegals, and helping them become citizens while urging them to vote for Democrats or their relatives won't get here. Is that too far-fetched? I don't think so.
Illegals broke our laws getting here and they are breaking them as they remain here. Start with those from Islamic countries and we may have the benefit of sweeping away some of those terrorist cells.