Wisconsin Gov. Scott Walker (R) speaks during a meeting on jobs and education at the National Governors Association convention Saturday, July 12, 2014, in Nashville, Tenn. (Mark Humphrey/AP)

Wisconsin Gov. Scott Walker (R) is running neck-and-neck against his leading Democratic challenger, according to a new poll released Wednesday.

The survey of likely voters, conducted by Marquette Law School, shows former Trek executive Mary Burke (D) leading Walker 47 percent to 46 percent. Her lead is well within the poll's margin of error. (In other words, consider it tied.)

In a May survey, Walker led Burke 48 percent to 45 percent. 

The new poll marks the first time Marquette has tested Walker's standing since news of Wisconsin prosecutors alleging the governor was part of a wide-ranging “criminal scheme” to coordinate the activities of conservative groups broke in June. A prosecutor later said through his attorney that Walker was not the target of an investigation into the alleged scheme.

The survey of 549 likely Wisconsin voters was conducted from July 17-20.