A look at key moments in the GOP debate

TAMPA, Fla. (AP) — Key moments in Monday night's GOP presidential debate:

Big moment:

To open the debate, Texas Gov. Rick Perry and former Massachusetts Gov. Mitt Romney immediately went after each other on Social Security — with Perry defending his inflammatory language and Romney accusing Perry of scaring seniors.

"It has been called a Ponzi scheme by many people long before me," Perry said. The Texas governor has also called the social safety net a "monstrous lie."

AP Photo/Chris O'Meara

Republican presidential candidates, from left, Utah Gov. Jon Huntsman, businessman Herman Cain, Rep. Mic...