In this Nov. 15, 2013 file photo, Tijuana-based tour guide Derrik Chinn, right, leads Michael Beverly and his wife Amanda, both of Newfoundland, Canada, on an evening walk along the Mexican side of the border as floodlights beam through the border structure from the United States side, in Tijuana, Mexico. To many Republican presidential contenders in Thursday, Aug. 8, 2015 debate, the U.S. border with Mexico must be secured for millions in the country illegally to stay. To many commuters at the nation’s busiest crossing, their border already is secure – even thriving by historical standards. (AP Photo/Gregory Bull)