It is not a deciding factor for much of anyone except the Pat Buchanan brigade. That amounted to about the same posting space here on FR in 2000 that you use today. It amounted to 1/3 of one percent on election day.
Take off those rose-colored glasses. Illegal immigration is a serious problem, it motivates the republican base, and you can bet a majority of Americans support a fence on the border and stoping illegal immigration.