Isn't it more complicated than a big wall if:

In a 2006 report, Pew estimated that "nearly half of all the unauthorized migrants now living in the United States entered the country legally through a port of entry such as an airport or a border crossing point where they were subject to inspection by immigration officials." While the source data gave an estimate that ranged from 33 percent to 50 percent, the report went middle-of-the-road and called it 45 percent.


Rubio says 40% of illegal immigrants stayed in the U.S. after their visas expired | PolitiFact Florida


Rubio thinks so. Trump doesn't.