In the poll conducted by the Democratic-leaning Public Policy Polling, 51 percent of likely voters said they approved of Walker, while 47 percent said they did not, the Milwaukee Journal Sentinel reported Sunday.
Forty-six percent of those polled said they view Barrett favorably and 46 percent said they did not.
Walker led among men, whites, and seniors, while Barrett led among women and young voters.
In a poll conducted by Marquette Law School, Walker led Barrett 52 percent to 45 percent.
A PPP poll conducted May 11-13 indicated Walker held a 50 percent-to-45 percent.
The latest PPP automated poll of 1,226 likely voters was conducted Saturday and Sunday. The margin of error is 2.8 percentage points.