Cain endorsed his fellow Georgian Saturday, just days before Florida's primary, at a GOP fundraiser.
Gingrich was also slated to speak to the group later Saturday night.
Gingrich, a former House speaker, is in a fierce fight for Tuesday's Florida's GOP primary with Mitt Romney.
Cain, a favorite of the tea party and a former pizza executive, left the race before the first nominating contests facing accusations of unwanted sexual advances. He remains popular, however, and would be a late boost for Gingrich.
