In the latest survey from conservative polling outlet Rasmussen, Romney leads with 37 percent, followed by Rick Santorum at 28 percent, Newt Gingrich at 17 percent and Ron Paul at 10 percent.
In the same poll last week, Romney led by 12 points over Santorum, 39 percent to 27 percent.
The 4 percent national gain for Santorum comes on the heels of Tuesday’s primary victories, in which the Romney campaign seemed to think it was poised to pull out at least one win in the Deep South, and raised expectations leading into the contests. Santorum ended up winning both Mississippi and Alabama, while Romney finished third in both.
Gallup’s five-day running average of polls produced a similar result, with Romney in the lead at 36 percent, followed by Santorum at 28 percent, Gingrich at 13 percent and Paul at 10 percent.
Gallup also found that Romney and Santorum were statistically tied as the second choice of voters who support Gingrich.
Forty percent of Gingrich supporters said Romney was their second choice, while 39 percent said Santorum.
Gingrich and Santorum have battled to position themselves as the conservative alternatives to Romney, and as Santorum has emerged as Romney’s primary challenger, many have speculated that Gingrich’s ongoing presence in the race was siphoning votes from the former Pennsylvania senator.
Recent close contests in Michigan and Ohio, both of which Romney won by a narrow margin, only amplified this sentiment, although the Gallup poll indicates that the effect may be overstated.
While Santorum has not directly called on Gingrich to drop out of the race, his associated super-PAC has.
Gingrich has said he intends to remain in the race all the way through to the Republican convention.