When Indiana State Treasurer Richard Mourdock won his Republican Senate primary last week, defeating six-term incumbent Sen. Dick Lugar, among his many congratulators was Herman Cain.

The former Godfather's Pizza CEO and brief Republican presidential co-front-runner, who now promotes his "9-9-9? tax plan through the group Cain Solutions,  endorsed Mourdock in August. Upon his victory, Cain praised Mourdock not only for having won  but also for having backed the 9-9-9 plan.

"By adopting my 9-9-9 plan, Richard Mourdock has shown he is committed to simple, commonsense solutions to the nation's biggest problems. I am proud the voters recognized this as well," Cain said in a  statement posted to the Cain Solutions website.

But Mourdock's campaign said he didn't adopt 9-9-9 per se.

The difference may be semantic, but 9-9-9 is not Mourock's chosen tax plan, although Mourdock supplied Cain with a positive statement on 9-9-9 ("Cain's 9-9-9 plan is a bold idea that needs to be part of the national debate on replacing the current tax code"),. And Cain also  lists Mourdock among a handful of 9-9-9 endorsers. In March, Cain announced Mourdock's decision to "formally adopt" 9-9-9, saying that Mourdock had "agreed to read and push for passage of the landmark tax reform legislation."

From the Mourdock camp, spokesman Chris Conner said in an email, "Richard Mourdock does believe that we need a major change in the federal tax code, which makes it flatter, fairer and broader," noting Mourdock's general praise for 9-9-9. "Our campaign, however, did not officially endorse Herman Cain's 9-9-9 Tax Plan."

Mourdock does support a consumption tax, Conner said, meaning he likes the most basic idea behind 9-9-9, which entails a 9 percent sales tax, a flat 9 percent income tax  and a flat 9 percent corporate tax. "Richard to date has not endorsed any specific tax plan - including VAT or the fair tax plan - but likes the broad concept of a consumption tax," Conner said.

For Cain Solutions, the difference between "endorsement" and "encouragement" is a small one. "Mr. Cain was thrilled with the idea that Mourdock is willing to even bring the debate on replacing the current tax code to Washington," Cain spokeswoman Kathy Hoekstra said.

Another of Cain's 9-9-9 supporters, former Florida senator and current Republican Senate candidate George LeMieux, also stopped short of offering a full endorsement. Cain on Thursday "announced the support of  U.S. Senate candidate George LeMieux for Cain's 9-9-9 Economic Recovery and Jobs Plan" in a press release on the Cain Solutions site.

In the same press release, LeMieux called 9-9-9 "one kind of reform that would be a definite improvement over our current existing tax system"; LeMieux offered that statement after Cain endorsed him at a Florida Lincoln Day dinner. Again, although LeMieux praised 9-9-9, his own tax plan is different: More similar to Mitt Romney's platform than to Cain's, LeMieux's Four Freedoms Plan calls for a 25 percent corporate tax and for "replac[ing] the outdated individual tax system with fewer brackets creating a flatter and fairer tax structure."

The other 9-9-9 endorsers, as listed by Cain Solutions, have "adopted" or "endorsed" 9-9-9 more explicitly, according to their campaigns. They include former congressman and current Michigan Republican Senate candidate Pete Hoekstra, North Dakota Republican Senate candidate Duane Sand  and Minnesota Republican Senate candidate Dan "Doc" Severson.