Those numbers represent a 5 percent gain in "acceptability" for Romney among GOP voters and a more dramatic 18 percentage point leap for Santorum since the last time the poll was released, at the beginning of last month. Each of the remaining Republican candidates saw his numbers fall, with Gingrich's 16-point drop ranking as the worst in the field.

Romney's cross-spectrum appeal should help him as he hopes to quickly sew up the GOP nomination and focus efforts on the general election. But the numbers also betray a dissatisfaction with the GOP field. In a CBS survey also released Tuesday, nearly six in 10 Republicans say they wish they had more options in the 2012 race.