He may have "stepped in it" by suffering a cringe-inducing memory lapse in the latest Republican presidential debate, but Rick Perry insisted Thursday he was still in the race despite a potentially campaign-ending gaffe.

"If there is a day to stay in the fight, this is it," he told NBC's "Today Show," defending his campaign when a reporter reminded him of messages flooding Twitter and social media that Perry's White House bid was likely doomed.

"We'll be in South Carolina on Saturday," the Texas governor said, referring to the next debate among the main Republican contenders for the chance to go up against President Barack Obama next November.

During the Wednesday debate in the US state of Michigan, Perry had struggled to remember a key plank of his economic platform, managing to name just two of the three US government departments he vowed to eliminate if he were elected.

"It's three agencies of government when I get there that are gone, Commerce, Education and the, err, what's the third one there..." Perry began, amid prompts from his seven rivals and gentle laughter from the audience.

"The third one, I can't, I'm sorry, I can't. Oops," he concluded.

Perry's team instantly sought to limit the damage after the debate, but by the morning after Perry was acknowledging his self-described "brain freeze" was a doozy.

"I don't mind saying clearly that I stepped in it last night," he told NBC with a smile. "I'm human like everyone else."

"The bottom line is, we're going to get up every day and go talk to the American people," he told ABC's "Good Morning America" as he made a rapid round of the early talk shows.

"They know that there's not a perfect candidate that's been made yet. And I'm kind of proof positive of it every day, that people make mistakes when they debate," he added.

And on CNN, he quipped: "I bet there are a lot of Americans out there who would like to forget some agencies of the government too," adding that the third mystery department he would eliminate, after Commerce and Education, was the Department of Energy.

Perry's debate debacle lit up the Twittersphere, with several political analysts weighing in, many saying his presidential viability is over.

Democratic strategist Paul Begala opined: "Perry's tiny brain freezes when he tries to name the 3 agencies he'd close. Mental midget shrinks even more."

Former president George W. Bush's spokesman Tony Fratto was equally blunt: "Perry can end his campaign right now," he Tweeted.