Aide: Gingrich can't win with Romney in the race

Hammond said Gingrich wouldn't be making any more appearances before Tuesday in Michigan or in Arizona, which votes the same day. Instead, Gingrich will focus on upcoming states where he can work to get a head start on Romney and rack up badly-needed delegates, including Tennessee, Oklahoma, Ohio and Gingrich's home state of Georgia.

And if Romney loses to Santorum in Michigan — the state where Romney grew up and his father served as governor — it would severely weaken the front-runner.

"Mitt Romney has to show up the day after Michigan and explain why he can't win his home state," Hammond said, dismissing questions about what Gingrich will say if he loses Georgia.

Gingrich has repeatedly dismissed calls for him to exit the race, even after Santorum's chain of February wins put him in a stronger position than Gingrich to claim he is the conservative alternative to Romney. He said after losing to Romney in Florida that he would continue the primary fight until the August nominating convention — unless Romney dropped out first.

But Hammond said Gingrich's strategy was to be the strongest candidate onstage, not to strengthen other candidates who could potentially foil Romney.

"We're not going to go out of our way to help Santorum," he said.