If you’ve been following Newt Gingrich’s attempts to regain the spotlight — for a third time — you know that he’s promising to bring gas prices down to $2.50. That’s a non-reality-based pledge that’s long on rhetoric and plays people for fools. So it’s no wonder Herman Cain is pom-poming the idea and giving it the “9-9-9” treatment.

Cain rode to the top of the Republican presidential heap on the back of his “9-9-9” tax plan. It was marketing genius. Simple. Easy to understand. Pity that the substance behind the plan didn’t make sense. Double pity that Cain himself couldn’t even explain it. But that’s not stopping him from sprinkling a little of his branding magic on Gingrich’s idea.

Folks, please welcome, “2-5-0.”

“I told him, because of the success of 9-9-9, you need a real simple, captivating way to tell the public what the objective is,” Cain told The Post’s Amy Gardner after an appearance with Gingrich yesterday in Chattanooga, Tenn. “His 2-5-0 idea is connecting and catching on, not just because he is putting that number on the table, but because he has a plan to get there. People are sick of generic responses to the problems we have. That is a very specific proposal. It’s doable, achievable and workable, and I think a lot of people are seeing he wasn’t afraid to put something like that on the table.”

Yes, people are sick of generic responses to the problems we have. Yet, they are also sick of politicians who make simple-minded promises that, it becomes clear later, don’t stand a chance of coming true. Increasing domestic energy production to make the United States energy-independent is the right goal. But Gingrich makes it sound like $2.50-a-gallon gasoline would come to a gas station near you if we were all unlucky enough to have him inaugurated president on Jan. 20, 2013.

Au contraire. All this increased domestic oil production will take a decade at least to bring online. In fact, a study released by the American Petroleum Institute shows that an all-of-the-above oil production strategy would garner “10 million barrels worth of added daily oil and natural gas production by 2030.” But in a CNN Money story from last month, Paul Bledsoe of the Bipartisan Policy Center zeroed in on the absurdity of Gingrich’s promise. “Obviously the price of oil is set on a global market,” he said. “In the immediate term there is almost nothing you can do.” He later added, “The notion that somehow we can produce so much domestically that we will move the global price is incorrect.”

But, hey, why let the facts and global commerce get in the way of a good slogan?