"For the second time in three weeks, the front-runner for the Democratic nomination wiped millions of dollars off the value of an industry."

Clinton tweeted: "We need to end private prisons. Protecting public safety...should never be outsourced or left to unaccountable corporations."

Corrections Corp. of America fell more than 6 percent, lopping off approximately $200 million in value, while GEO Group Inc. dropped 4.2 percent, losing about $100 million.