Romney, a former Massachusetts governor, held a 23 percentage point lead over former House Speaker Gingrich as recently as Jan. 11-15. The Princeton, N.J., polling agency said Romney dropped 8 percentage points and Gingrich picked up 14 percentage points among registered Republicans voters in a week's time.
Gingrich beat Romney in Saturday's South Carolina Republican primary. The Florida primary is Tuesday.
For perspective, Gallup said in polling conducted in September Romney led Gingrich by as many as 19 percentage points nationally, then Gingrich surged ahead to a 15 percentage point lead over Romney in early December. Gingrich's support then fell throughout December and Romney regained support after his near-win in Iowa and his victory in the New Hampshire primary.
Results are based on nationwide telephone interviews with 1,221 Republican registered voters conducted as part of Gallup Daily tracking Wednesday through Sunday. The margin of error is 4 percentage points.
Notable deaths of 2014 [PHOTOS]