October 2007 may turn out to be the month that immigration became a key issue in presidential politics. It hasn't been, at least in my lifetime. The Immigration Act of 1965, which turned out to open up America to mass immigration after four decades of restrictive laws, wasn't one of the Great Society issues Lyndon Johnson emphasized in 1964. The Immigration Act of 1986, which legalized millions of illegal immigrants but whose border and workplace provisions have never been effectively enforced, was a bipartisan measure unmentioned in the debates between Ronald Reagan and Walter Mondale. There was no perceptible difference...