Romney, a former Massachusetts governor who collected a decisive victory in the Arizona GOP primary and a much closer win in Michigan Tuesday, leads the latest Rasmussen Reports national telephone survey of likely Republican primary voters with 40 percent, followed by Santorum, a former U.S. senator from Pennsylvania, with 24 percent. Former House Speaker Newt Gingrich was third with 16 percent and Texas Congressman Ron Paul fourth with 12 percent.
Santorum led the Rasmussen poll two weeks ago with 39 percent to 27 percent for Romney.
Romney bested Santorum 35 percent to 24 percent in Gallup's national survey. Gingrich and Paul had 15 percent and 11 percent, respectively.
Rasmussen polled 1,000 likely GOP primary voters Feb. 29, reporting an error margin of 3 percentage points.
Gallup's poll is a five-day rolling average that does not include a margin of error.