Mitt Romney and Rick Perry clashed over Social Security at the CNN/Tea Party Republican debate on Monday night.

Romney pointed out that in his book, Fed Up, Perry called Social Security an "unconstitutional" program and a total failure.

"If what you’re trying to say is that back in the ’30s and ’40s that the government made all the right decisions, I disagree with you," Perry responded. "It’s time for us to get back to the Constitution and a program that’s been there 70 or 80 years, obviously we’re not going to take that program away. But for people to stand up and support what they did in the '30s or what they're doing in the 2010's is not appropriate for America."

Later in the debate, Perry said he would not repeal Medicare Part D, the prescription drug program. In response, Romney's campaign quickly sent out an email noting that in his book, Perry "sharply opposed" the program.

In last week's NBC Republican debate, the two candidates similarly clashed over job creation.

Watch video, courtesy of CNN, below: