MADISON, Wis. (AP) — Less than a month before the Aug. 14 primary, roughly a third of voters are still undecided in Wisconsin's Democratic primary for governor and Republican contest for U.S. Senate.

The latest Marquette University Law School poll released Wednesday shows 30 percent are undecided in the Senate race, unchanged from last month. Thirty-eight percent are undecided in the Democratic primary, up from 34 percent last month.

Among the eight Democratic gubernatorial candidates, Tony Evers led with 31 percent support and the rest of the field around 5 percent.

On the Republican side, Leah Vukmir has overtaken Kevin Nicholson 34 percent to 32 percent. It's the first time she's led in this current poll cycle. She was down 32 percent to 37 percent in June and 19 percent to 28 percent in March. 

The poll surveyed 800 registered voters between July 11 and Sunday. It has a margin of error of plus or minus 4.1 percentage points, although that increases to 6.6 percentage points for questions targeting Democratic primary voters and 7 percentage points for Republicans.