Wisconsin Gov. Scott Walker (R) leads Democratic challenger Mary Burke in a new poll released Wednesday that shows a drop in Walker's approval rating.

Walker leads Burke 48 percent to 41 percent among Wisconsin voters in the Marquette Law School poll, unchanged from the previous survey. But the governor's approval rating has slipped from 51 percent down to 47 percent. His disapproval rating is now 47 percent, up from 42 percent.

The survey is the first test of public opinion since a the release of more than 25,000 pages of e-mails last month involving Walker's office when he was county executive of Milwaukee. Democrats seized on the e-mails to portray the governor in an unflattering light and raise questions about the conduct of his campaign and official aides, who were regularly in touch, according to an investigator.

Walker was not charged in the case involving the e-mails, nor was he a target of the investigation.

Sixty-seven percent of voters say they have heard about the e-mail release. Among them, 43 percent say the e-mails gave them a less favorable view of the governor while 53 percent say it made no difference in the way they view him.

The poll of 801 Wisconsin voters was conducted March 20-23. It carries a margin of error of of +/- 3.5 percentage points.