The latest independent statewide poll shows Democratic challenger Bob Casey with a slight lead over Republican incumbent Rick Santorum in their hotly contested Senate race.

The poll found 45 percent of the voters questioned supported Casey, the state treasurer, while 39 percent supported Santorum, the No. 3 Senate Republican.

The poll of 550 registered voters was conducted from July 31 to Aug. 3 by The Morning Call of Allentown and the Muhlenberg College Institute of Public Opinion. The poll results carry a sampling error margin of plus or minus 4 percentage points.

The poll, which appeared in Sunday editions of The Morning Call, found 43 percent viewed Santorum favorably and 34 percent unfavorably, compared to a 42-38 favorable-unfavorable split in March.

Casey notched a 39 percent favorability rating and a 21 percent unfavorable score, compared with a 38-18 split in March.

In mid-June, a Quinnipiac University poll of 1,076 registered voters found Casey with a 52 percent to 34 percent lead over Santorum.

In the governor's race, the new poll found Democratic Gov. Ed Rendell holds a 16-point lead over Republican challenger Lynn Swann, compared with only a slight advantage in April. Rendell had support from 51 percent of those surveyed and Swann 35 percent, compared to Rendell's 45-39 lead in late April.