Former Republican presidential candidate Newt Gingrich warned in a recent interview that a handful of billionaires had an "unfair advantage" in choosing the next president of the United States.

Gingrich told ABC News in an interview posted on Tuesday why presumptive Republican nominee Mitt Romney came out on top during the GOP primaries: "In the end, he had, I think, sixteen billionaires and we had one."

"We're in a situation where if you're really rich, you have an enormous, and I think unfair, advantage," the former House Speaker explained. "The trick is not to cripple the rich, the trick is to empower the middle class."

Gingrich's one billionaire was casino mogul Sheldon Adelson, who gave about $25 billion to his election effort. Adelson is now on team Romney, promising to give as much as $100 million to help the candidate defeat President Barack Obama.

"Look, I've told my supporters, this is the most important election of our lifetime," Gingrich said. "Any conservative who sits on the sidelines is helping re-elect Barack Obama, and I think an Obama second term, for our values, would be a nightmare."

But the Georgia Republican says that the president has the right to go after Romney's record at Bain Capital just as he did with the help of Adelson in the primary.

"They're legitimate questions to ask, and I think you should be able to ask about anybody," Gingrich remarked. "It was a very tough primary, and we fought each other. I threw the kitchen sink at him, he threw a bigger kitchen sink at me."

When it comes to a job in a potential Romney administration, Gingrich joked that he's not ruling out a role as "Secretary of Zoos and Museums."

"I find myself renewed at zoos," he added. "Elephants are among my favorite, partly because I'm Republican, partly because I'm big and elephants make me feel like I'm the right size."