ABC’s Michael Falcone and Arlette Saenz report:

In the post-”oops” world, it’s worth recalling a few times when Rick Perry’s memory did not fail him like it did on live television at Wednesday’s night’s presidential debate in Michigan.

Just a little over a month ago Perry was able to name the Department of Energy as one of the agencies he would eliminate if elected president at a town hall meeting in Hampton, N.H.

“The Department of Energy,” Perry began in response to a voters’ question. “They’ve never created one bit of energy the best I can tell. Our energy industry needs to be freed up from the over regulation.”

According to coverage of the Oct. 1 event, Perry identified the Department of Education as well: “You ask yourself why do we have a federal education agency? Why do we have a Department of Education?”

Perry also named both Energy and Education as departments he wanted to get rid of at a Labor Day town hall meeting in South Carolina and he did so again at a presidential debate in Tampa, Fla. on Sept. 12.

“What we need to do is cut the Department of Education, Department of Energy,” Perry said to cheers, “and all these departments and get rid of them.”

At Wednesday night’s debate during a moment that has reinforced the idea that Perry is a weak debater, the Texas governor threw one more agency onto his hit list: the Department of Commerce.

“It’s three agencies of government when I get there that are gone,” Perry said. “Commerce, Education and the um, what’s the third one there?” (That’s when things took a turn for the worse as Perry tried for nearly a minute to name the third agency — the Department of Energy. Perry ultimately failed to come up with the name.)

Sources at the Perry campaign say they do not believe that the Texas governor has ever mentioned all three departments in one breath and that his decision to mention Commerce Wednesday night was new.

ABC’s Barbara Friedman contributed reporting.