Republican presidential hopeful Rick Perry says he would eliminate three federal agencies. Just don't ask him to name them.

"Commerce, Education and the what's the third one there? Let's see," the Texas governor said during a debate Wednesday night.

Perry's rivals tried to bail him out, suggesting the Environmental Protection Agency.

"EPA, there you go," Perry said, seemingly taking their word for it.

But that wasn't it. And when pressed, the candidate drew another blank.

"Seriously?" moderator John Harwood, one of CNBC's debate hosts, asked. "You can't name the third one?"

"The third agency of government I would do away with the Education, the Commerce. And let's see. I can't. The third one, I can't," Perry said. "Oops."

Later in the debate, Perry revisited the question and said he meant to call for the elimination of the Energy Department.

HuffPost's Jon Ward reports :

Perry has already been beset by unforced errors in his less than three months as a presidential candidate, but this topped all of his previous gaffes. It was a moment that very well might have extinguished his chances of coming back and competing with Romney.

The Texan -- who has admitted he is not a good debater -- nonetheless entered the night needing to dramatically elevate his performance in these settings and to at least demonstrate a certain level of competence and command of the issues.

Instead, Perry's jaw-dropping memory lapse created a solid minute of full-color video memorializing the governor as a bumbling joke.

Perry knew he had made a serious mistake, and for the first time in nine debates he came to speak with reporters in the filing center after the debate.

"Yeah I stepped in it man. Yeah it was embarrassing. Of course it was," he said. "But here's what's more important. People understand that our principles, our conservative principles, are what matter."

Click here to read more on Perry's misstep. Below, a video recap of Wednesday night's debate.

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