But Gingrich said Wednesday morning he'll press ahead, and will "wait and see how the race goes."
Appearing on Bob Bennett's "Morning in America" radio program, Gingrich said he would have left the race if he had lost Georgia.
He also said there's no evidence that Santorum could defeat Romney, even in a one-on-one competition. Gingrich said if he were convinced that Santorum was a "slam dunk to beat Romney and to beat Obama," he would "really consider getting out."
Gingrich's win in Georgia, which he represented for several terms in Congress, was his first victory since he captured the South Carolina primary in January.
Campaigning Wednesday in Alabama, Gingrich portrayed Romney as a moderate along the lines of losing GOP candidates Bob Dole and John McCain.
As for Santorum, Gingrich cast him as a creature of Washington who was willing to play along with the team.
Gingrich told supporters, "I am not going to Washington to be a good team member. I am going to Washington to change Washington."
A Gingrich spokesman said Alabama and Mississippi, which vote next week, are must-win states for the former House speaker.
Meanwhile, Romney supporters are making the case that it is time for Republicans to close ranks around him. House Majority Leader Eric Cantor told CBS that Romney's claim to the nomination is inevitable. Former New York Gov. George Pataki, on Fox News, endorsed Romney and said it's time for Republicans to stop sniping at each other and to focus on Obama.
The Red, White and Blue Fund has spent about $3 million on TV ads to help Santorum's White House bid.