CHATTANOOGA, Tenn. — Georgia businessman Herman Cain on Monday hailed Newt Gingrich’s promise to push the price of a gallon of gas under $2.50 as the new “9-9-9” of the presidential campaign -- another catchy yet substantive slogan, he said, that gives voters a concrete promise of action.

Appearing with Gingrich at an airport rally here late Monday, Cain said Gingrich’s “250gas” campaign, memorialized on placards and on Twitter and Facebook, is catching on across the country. Cain also said he encouraged the former speaker, whom he endorsed in January after his own departure from the presidential field, to boil his energy plan down to a simple numeric slogan much like his own, hugely popular 9-9-9 tax plan.

Cain also gave the gasoline proposal a new, even catchier sound: “Two-Five-Zero.”

“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 said in a short interview following his appearance with Gingrich. “His Two-Five-Zero 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.”

Cain campaigned for Gingrich in Tennessee on Friday, Saturday and again Monday, and the businessman said the response has been huge. He said Gingrich has only to win Georgia on Super Tuesday to continue on, but Cain won’t be surprised by a better-than-expected showing in Tennessee as well, where the latest polls show Gingrich catching up to leading rivals Rick Santorum and Mitt Romney.

“With us being here, it says to people, ‘We are not giving up,’ ” Cain said. “ ‘We can win. Don’t believe the media hype about who is supposed to win. Vote for who you believe should win.’ ”

Gingrich has been talking about what he views as the too-high price of gas for years, but he has stepped up his rhetoric in recent weeks, describing his plan for energy independence as a centerpiece of his candidacy and a central distinction not only between him and his Republican rivals but between him and President Obama, too.

Gingrich promises to unleash the United States’ own energy reserves by allowing more exploration of all sources. The policy makes economic sense because it would lower the price of gas, he says; and it makes strategic sense because it would eliminate the nation’s dependence on foreign oil -- and thus many of the American foreign-policy troubles with such oil-rich regions as the Middle East.

One of Gingrich’s most common lines on the campaign trail, and one that most often elicits cheers from his audience, is a pledge that an American president should never again bow to a Saudi king. It is a reference to a meeting between Obama and King Abdullah of Saudi Arabia at a G-20 gathering in London in 2009. Conservative critics claimed that the video coverage shows Obama bowing, but the White House said at the time that wasn’t true.