Some debate screw-ups are so memorable, they practically become iconic. Gerald Ford claiming there was “no Soviet domination of Eastern Europe,” Dan Quayle comparing himself to JFK, and James Stockdale asking who he is and what he’s doing there were all pretty unforgettable.

And it looks like Rick Perry joined them last night. In the unlikely event you haven’t already seen the Texas governor’s brain freeze, here’s the clip:

Perry’s answer was going reasonably well right up until he started listing the “three agencies of government … that are gone” under a Perry administration. Commerce was first, education was second, and then the governor simply couldn’t think of a third.

As Perry struggled, Mitt Romney chimed in, trying to give him a hand, asking if EPA was the third. The Texan vowed to “rebuild” the EPA, but said that wasn’t it.

After trying and failing several more times to list them, Perry could only name education, then remembered commerce while checking his notes. Pressed by John Harwood for the rest of his list, the governor concluded, “The third one, I can’t. Sorry. Oops.”

Later, Perry said he was trying to remember the Department of Energy, but forgot it. “I’m glad I had my boots on tonight,” he told reporters after the debate. “I stepped in it out there.” Perry added, however, that he will not skip the debate in South Carolina, scheduled for Saturday.

Needless to say, this is not what Rick Perry needed. Unless there’s a strong contingent of Republican voters who vote based on which candidate they most feel sorry for, the “oops” moment puts Perry’s entire campaign in jeopardy.

It’s not just because of his mental lapse. Arizona Gov. Jan Brewer (R), during a debate last year, completely blanked for a painfully long time, but nevertheless maintained her support and won fairly easily.

So why was last night so much more damaging to Perry? Because it reinforced the party’s biggest fears about his candidacy. For two months, Republicans have said the governor seems unprepared, unqualified, and at times, simply ignorant. Party leaders have thought about the prospect of him going up against President Obama next year, and recoiled. Perry needed to demonstrate last night that he’s ready for prime time, and instead, he failed to remember the three cabinet agencies he wants to eliminate.

Some Republicans have been looking for an excuse to give up on his flailing campaign, and last night, Perry gave them one.

And on a more substantive note, it’s also worth noting that the underlying policy goal that Perry was trying to articulate happens to be a horrible idea in its own right.

How does Perry recover from this? In all likelihood, he can’t. Perry was already moving in the wrong direction, and with the window of opportunity closing, the governor will effectively have to hope that every other GOP candidate gets ensnared in a massive scandal, all at the same time. As Jon Chait joked, “Unless Perry happens to leap in front of a bullet intended for Nancy Reagan, there’s simply nothing he can do to atone for the cumulative damage he has done himself.”

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.