MCALLEN, TX - AUGUST 07: U.S. Border Patrol agents detain undocumented immigrants after they crossed the border from Mexico into the United States on August 7, 2015 in McAllen, Texas. The state's Rio Grande Valley corridor is the busiest illegal border crossing into the United States. Border security and immigration have become major issues in the U.S. presidential campaigns. (Photo by John Moore/Getty Images)
