Much has been made about the supposed $3.4 million ad buy in South Carolina by Newt Gingrich’s super PAC, Winning the Future. The super PAC is being bankrolled by Las Vegas casino tycoon Sheldon Adleson. But, in fact, the super PAC hasn’t spent a fraction of that amount. Sources provide this breakdown of ad purchases in South Carolina through Jan. 17:

Red White Blue (Santorum) - $11,450

Restore Our Future (Romney) - $690,095

Santa Rita (Paul) - $135,583

Winning Our Future (Gingrich) - $700,780

In other words, perhaps there is more bark than bucks behind Gingrich’s super PAC. It may well be that Gingrich’s backers are none too eager to keep throwing good money after bad. I spoke to a Republican donor who is a friend of Adelson. He told me, “I cannot imagine Sheldon Adelson is going to go through with this. Newt has embarrassed him. Sheldon Adelson is personally a tremendous free enterprise success story. And for him to see his money used to fund left-wing, anti-business language has to be very painful.” Adelson’s friend added that Adelson’s own rags-to-riches story and longtime support of conservative causes are entirely at odds with the Gingrich onslaught.

Gingrich will no doubt soldier on, bringing what is now almost entirely a negative message to South Carolina about Mitt Romney. But at some point, he becomes a non-factor in the race, and the anti-Bain charges become old news. To the extent that Gingrich continues to decline in the South Carolina polls and conservatives keep rallying to defend Bain, the Romney team is probably pleased to have Gingrich stick around.

Americans for Prosperity is the latest conservative outfit to go after the anti-Bain attack, in a statement that read, in part:

“Republican candidates who believe in the free market know better than to adopt the misguided and disingenuous tactics employed by those on the far left, which demonize successful entrepreneurs and stir up discontent to be used as a political tool.

“The American people want an honest and robust debate, not political gimmicks. We urge all presidential candidates — including President Obama — to stand down from this kind of divisive class-warfare rhetoric, and instead focus on offering their own unique solutions to get Americans working again, support free market enterprise, and restore confidence in the marketplace. Citizens of the United States are in the process of choosing their next President, and deserve the best, honest effort from each candidate.”

Indeed, given how animated Romney was last night, you can imagine he’d relish a chance in the debates to say something like that to Gingrich and the other anti-Bain hangers-on.